问如何在Django FeinCMS项目中子类化我的ModelAdmins？

EN

class Faked(object):
    "A fake class to use to stand in for True in ExtendableModelAdminMixin."
    pass


class ExtendableModelAdminMixin(object):
    """ModelAdmin mixin to allow ModelAdmins to be extended (i.e.
subclassed) without messing
    up the Feincms extension registering mechanism.

    Technical note: the reason we do this is because otherwise references
    get preserved across different ModelAdmins, which means the ModelAdmins
    fail Django's checks.
    The straightforward declarative syntax of ModelAdmins sets
    attributes at the class level, but FeinCMS's
    initialize_extensions() method overrides them on the
    instance level.  So in our mixin we do a deepcopy of any
    instance level attributes before initializing the extensions.
    """
    def __init__(self, *args, **kwargs):
        # Set the _extensions_initialized attribute to prevent
        # extensions being initialized just yet
        self._extensions_initialized = Faked
        super(ExtendableModelAdminMixin, self).__init__(*args, **kwargs)

        # Before running extensions, copy any lists so we don't
        # preserve references across different ModelAdmin subclasses
        # TODO - include any other ModelAdmin properties that
        # are causing issues.
        for attr_name in ('list_display',
                          'fieldsets',
                          'search_fields', 'list_filter'):
            original = getattr(self, attr_name, [])
            copied_attr = deepcopy(original)
            setattr(self, attr_name, copied_attr)

        # Now we're ready to initialize extensions
        del(self._extensions_initialized)
        self.initialize_extensions()

class SharedModelAdmin(ExtendableModelAdmin, ItemEditor):
    # Declare some defaults here, as usual
    list_display = ['field_one', 'field_two']

class MyModelAdmin(SharedModelAdmin):
    def __init__(self, *args, **kwargs):
        super(MyModelAdmin, self).__init__(*args, **kwargs)
        # Override things at the instance level
        self.list_display += ['field_three']