221 lines
8.4 KiB
Python
221 lines
8.4 KiB
Python
"""
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XML serializer.
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"""
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from django.conf import settings
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from django.core.serializers import base
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from django.db import models
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from django.utils.xmlutils import SimplerXMLGenerator
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from xml.dom import pulldom
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class Serializer(base.Serializer):
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"""
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Serializes a QuerySet to XML.
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"""
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def start_serialization(self):
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"""
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Start serialization -- open the XML document and the root element.
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"""
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self.xml = SimplerXMLGenerator(self.stream, self.options.get("encoding", settings.DEFAULT_CHARSET))
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self.xml.startDocument()
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self.xml.startElement("django-objects", {"version" : "1.0"})
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def end_serialization(self):
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"""
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End serialization -- end the document.
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"""
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self.xml.endElement("django-objects")
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self.xml.endDocument()
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def start_object(self, obj):
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"""
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Called as each object is handled.
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"""
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if not hasattr(obj, "_meta"):
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raise base.SerializationError("Non-model object (%s) encountered during serialization" % type(obj))
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self.xml.startElement("object", {
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"pk" : str(obj._get_pk_val()),
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"model" : str(obj._meta),
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})
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def end_object(self, obj):
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"""
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Called after handling all fields for an object.
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"""
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self.xml.endElement("object")
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def handle_field(self, obj, field):
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"""
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Called to handle each field on an object (except for ForeignKeys and
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ManyToManyFields)
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"""
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self.xml.startElement("field", {
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"name" : field.name,
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"type" : field.get_internal_type()
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})
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# Get a "string version" of the object's data (this is handled by the
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# serializer base class). None is handled specially.
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value = self.get_string_value(obj, field)
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if value is not None:
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self.xml.characters(str(value))
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self.xml.endElement("field")
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def handle_fk_field(self, obj, field):
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"""
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Called to handle a ForeignKey (we need to treat them slightly
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differently from regular fields).
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"""
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self._start_relational_field(field)
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related = getattr(obj, field.name)
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if related is not None:
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self.xml.characters(str(related._get_pk_val()))
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else:
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self.xml.addQuickElement("None")
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self.xml.endElement("field")
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def handle_m2m_field(self, obj, field):
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"""
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Called to handle a ManyToManyField. Related objects are only
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serialized as references to the object's PK (i.e. the related *data*
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is not dumped, just the relation).
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"""
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self._start_relational_field(field)
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for relobj in getattr(obj, field.name).iterator():
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self.xml.addQuickElement("object", attrs={"pk" : str(relobj._get_pk_val())})
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self.xml.endElement("field")
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def _start_relational_field(self, field):
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"""
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Helper to output the <field> element for relational fields
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"""
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self.xml.startElement("field", {
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"name" : field.name,
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"rel" : field.rel.__class__.__name__,
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"to" : str(field.rel.to._meta),
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})
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class Deserializer(base.Deserializer):
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"""
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Deserialize XML.
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"""
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def __init__(self, stream_or_string, **options):
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super(Deserializer, self).__init__(stream_or_string, **options)
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self.encoding = self.options.get("encoding", settings.DEFAULT_CHARSET)
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self.event_stream = pulldom.parse(self.stream)
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def next(self):
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for event, node in self.event_stream:
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if event == "START_ELEMENT" and node.nodeName == "object":
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self.event_stream.expandNode(node)
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return self._handle_object(node)
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raise StopIteration
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def _handle_object(self, node):
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"""
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Convert an <object> node to a DeserializedObject.
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"""
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# Look up the model using the model loading mechanism. If this fails, bail.
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Model = self._get_model_from_node(node, "model")
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# Start building a data dictionary from the object. If the node is
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# missing the pk attribute, bail.
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pk = node.getAttribute("pk")
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if not pk:
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raise base.DeserializationError("<object> node is missing the 'pk' attribute")
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data = {Model._meta.pk.name : pk}
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# Also start building a dict of m2m data (this is saved as
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# {m2m_accessor_attribute : [list_of_related_objects]})
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m2m_data = {}
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# Deseralize each field.
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for field_node in node.getElementsByTagName("field"):
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# If the field is missing the name attribute, bail (are you
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# sensing a pattern here?)
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field_name = field_node.getAttribute("name")
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if not field_name:
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raise base.DeserializationError("<field> node is missing the 'name' attribute")
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# Get the field from the Model. This will raise a
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# FieldDoesNotExist if, well, the field doesn't exist, which will
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# be propagated correctly.
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field = Model._meta.get_field(field_name)
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# As is usually the case, relation fields get the special treatment.
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if field.rel and isinstance(field.rel, models.ManyToManyRel):
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m2m_data[field.name] = self._handle_m2m_field_node(field_node)
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elif field.rel and isinstance(field.rel, models.ManyToOneRel):
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data[field.name] = self._handle_fk_field_node(field_node)
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else:
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value = field.to_python(getInnerText(field_node).strip().encode(self.encoding))
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data[field.name] = value
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# Return a DeserializedObject so that the m2m data has a place to live.
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return base.DeserializedObject(Model(**data), m2m_data)
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def _handle_fk_field_node(self, node):
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"""
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Handle a <field> node for a ForeignKey
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"""
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# Try to set the foreign key by looking up the foreign related object.
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# If it doesn't exist, set the field to None (which might trigger
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# validation error, but that's expected).
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RelatedModel = self._get_model_from_node(node, "to")
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# Check if there is a child node named 'None', returning None if so.
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if len(node.childNodes) == 1 and node.childNodes[0].nodeName == 'None':
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return None
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else:
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return RelatedModel.objects.get(pk=getInnerText(node).strip().encode(self.encoding))
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def _handle_m2m_field_node(self, node):
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"""
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Handle a <field> node for a ManyToManyField
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"""
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# Load the related model
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RelatedModel = self._get_model_from_node(node, "to")
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# Look up all the related objects. Using the in_bulk() lookup ensures
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# that missing related objects don't cause an exception
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related_ids = [c.getAttribute("pk").encode(self.encoding) for c in node.getElementsByTagName("object")]
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return RelatedModel._default_manager.in_bulk(related_ids).values()
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def _get_model_from_node(self, node, attr):
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"""
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Helper to look up a model from a <object model=...> or a <field
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rel=... to=...> node.
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"""
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model_identifier = node.getAttribute(attr)
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if not model_identifier:
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raise base.DeserializationError(
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"<%s> node is missing the required '%s' attribute" \
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% (node.nodeName, attr))
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try:
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Model = models.get_model(*model_identifier.split("."))
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except TypeError:
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Model = None
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if Model is None:
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raise base.DeserializationError(
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"<%s> node has invalid model identifier: '%s'" % \
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(node.nodeName, model_identifier))
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return Model
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def getInnerText(node):
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"""
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Get all the inner text of a DOM node (recursively).
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"""
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# inspired by http://mail.python.org/pipermail/xml-sig/2005-March/011022.html
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inner_text = []
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for child in node.childNodes:
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if child.nodeType == child.TEXT_NODE or child.nodeType == child.CDATA_SECTION_NODE:
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inner_text.append(child.data)
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elif child.nodeType == child.ELEMENT_NODE:
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inner_text.extend(getInnerText(child))
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else:
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pass
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return "".join(inner_text) |