'Get a form Field for a ManyToManyField.'

def formfield_for_manytomany(self, db_field, request=None, **kwargs):

    if (not db_field.rel.through._meta.auto_created):
        return None
    db = kwargs.get('using')
    if (db_field.name in self.raw_id_fields):
        kwargs['widget'] = widgets.ManyToManyRawIdWidget(db_field.rel, self.admin_site, using=db)
        kwargs['help_text'] = ''
    elif (db_field.name in (list(self.filter_vertical) + list(self.filter_horizontal))):
        kwargs['widget'] = widgets.FilteredSelectMultiple(db_field.verbose_name, (db_field.name in self.filter_vertical))
    if (not ('queryset' in kwargs)):
        queryset = self.get_field_queryset(db, db_field, request)
        if (queryset is not None):
            kwargs['queryset'] = queryset
    return db_field.formfield(**kwargs)
