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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _check_validity(self):
 """Checks the validity of the state element's properties Some validity checks can only be performed by the parent. Thus, the existence of a parent and a check function must be ensured and this function be queried. :return: validity and messages :rtype: bool, str """

        from rafcon.core.states.state import State

        if not self.parent:
            return True, "no parent"
        if not isinstance(self.parent, State):
            return True, "no parental check"
        return self.parent.check_child_validity(self)