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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 trustRootValid(self):
 """Is my return_to under my trust_root? @returntype: bool """

        if not self.trust_root:
            return True
        tr = TrustRoot.parse(self.trust_root)
        if tr is None:
            raise MalformedTrustRoot(self.message, self.trust_root)

        if self.return_to is not None:
            return tr.validateURL(self.return_to)
        else:
            return True