def is_unitary(self, atol=None, rtol=None):
try:<EOL><INDENT>op = self.to_operator()<EOL>return op.is_unitary(atol=atol, rtol=rtol)<EOL><DEDENT>except QiskitError:<EOL><INDENT>return False<EOL><DEDENT>
Return True if QuantumChannel is a unitary channel.