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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 is_derived_from(self, identity: QualName, base: QualName) -> bool: """Return ``True`` if `identity` is derived from `base`."""

        try:
            bases = self.identity_adjs[identity].bases
        except KeyError:
            return False
        if base in bases:
            return True
        for ib in bases:
            if self.is_derived_from(ib, base):
                return True
        return False