Fixed #6266: Added note to docs/modelforms.txt pointing out that they're just standard forms and have all the same methods as standard forms

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7305 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/modelforms.txt

@@ -231,6 +231,16 @@ For example::
     # Create and save the new author instance. There's no need to do anything else.
     >>> new_author = f.save()
 
+Other than the ``save()`` and ``save_m2m()`` methods, a ``ModelForm``
+works exactly the same way as any other ``newforms`` form. For
+example, the ``is_valid()`` method is used to check for validity, the
+``is_multipart()`` method is used to determine whether a form requires
+multipart file upload (and hence whether ``request.FILES`` must be
+passed to the form), etc.; see `the standard newforms documentation`_
+for more information.
+
+.. _the standard newforms documentation: ../newforms/
+
 Using a subset of fields on the form
 ------------------------------------