Fixed #21908 -- Added example usage for ModelAdmin.get_inline_instances().

    ``obj`` being edited (or ``None`` on an add form) and is expected to return

    a ``list`` or ``tuple`` of :class:`~django.contrib.admin.InlineModelAdmin`

    objects, as described below in the :class:`~django.contrib.admin.InlineModelAdmin`

    section.

    section. For example, the following would return inlines without the default

    filtering based on add, change, and delete permissions::

        class MyModelAdmin(admin.ModelAdmin):

            def get_inline_instances(request, obj=None):

                return [inline(self.model, self.admin_site) for inline in self.inlines]

.. method:: ModelAdmin.get_urls()