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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 all_hermitian(self):
 """ Check if all basis operators are hermitian. """

        if self._all_hermitian is None:
            _log.debug("Testing and caching if all basis operator are hermitian")
            self._all_hermitian = all((is_hermitian(op) for op in self.ops))
        return self._all_hermitian