def formfield_for_dbfield(self, db_field, **kwargs):
        request = kwargs.pop("request", None)

        # If the field specifies choices, we don't need to look for special
        # admin widgets - we just need to use a select widget of some kind.
        if db_field.choices:
            return self.formfield_for_choice_field(db_field, request, **kwargs)

        # ForeignKey or ManyToManyFields
        if isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            # Combine the field kwargs with any options for formfield_overrides.
            # Make sure the passed in **kwargs override anything in
            # formfield_overrides because **kwargs is more specific, and should
            # always win.
            if db_field.__class__ in self.formfield_overrides:
                kwargs = dict(self.formfield_overrides[db_field.__class__], **kwargs)

            # Get the correct formfield.
            if isinstance(db_field, models.ForeignKey):
                formfield = self.formfield_for_foreignkey(db_field, request, **kwargs)
            elif isinstance(db_field, models.ManyToManyField):
                formfield = self.formfield_for_manytomany(db_field, request, **kwargs)

            # For non-raw_id fields, wrap the widget with a wrapper that adds
            # extra HTML -- the "add other" interface -- to the end of the
            # rendered output. formfield can be None if it came from a
            # OneToOneField with parent_link=True or a M2M intermediary.
            if formfield and db_field.name not in self.raw_id_fields:
                related_modeladmin = self.admin_site._registry.get(
                                                            db_field.rel.to)
                can_add_related = bool(related_modeladmin and
                            related_modeladmin.has_add_permission(request))
                formfield.widget = widgets.RelatedFieldWidgetWrapper(
                            formfield.widget, db_field.rel, self.admin_site,
                            can_add_related=can_add_related)

            return formfield

        # If we've got overrides for the formfield defined, use 'em. **kwargs
        # passed to formfield_for_dbfield override the defaults.
        for klass in db_field.__class__.mro():
            if klass in self.formfield_overrides:
                kwargs = dict(copy.deepcopy(self.formfield_overrides[klass]), **kwargs)
                return db_field.formfield(**kwargs)

        # For any other type of field, just call its formfield() method.
        return db_field.formfield(**kwargs)
Hook for specifying the form Field instance for a given database Field
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/contrib/admin/options.py/BaseModelAdmin.formfield_for_dbfield