def _check_cargs(self, cargs):
        """Raise exception if clbit is not in this circuit or bad format."""
        if not all(isinstance(i, tuple) and
                   isinstance(i[0], ClassicalRegister) and
                   isinstance(i[1], int) for i in cargs):
            raise QiskitError("carg not (ClassicalRegister, int) tuple")
        if not all(self.has_register(i[0]) for i in cargs):
            raise QiskitError("register not in this circuit")
        for clbit in cargs:
            clbit[0].check_range(clbit[1])
Raise exception if clbit is not in this circuit or bad format.