<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parent(self):
 """ Cache a instance of self parent class. :return object: instance of self.Meta.parent class """

        if not self._meta.parent:
            return None

        if not self.__parent__:
            self.__parent__ = self._meta.parent()

        return self.__parent__