使用类mixin导致Pycharm对null=True说“意外参数”

Pycharm在使用时显示“意外参数” CIEmailField(null=True) CIEmailFieldOld(null=True) . null

from django.db.models import *

class CIText:
    def db_type(self, connection):
        return 'citext'

class CIEmailField(CIText, EmailField):
    pass

class CIEmailFieldOld(EmailField):
    def db_type(self, connection):
        return 'citext'