def operation_at(self, qubit: raw_types.Qid) -> cirq.Operation | None:
        """Returns the operation on a certain qubit for the moment.

        Args:
            qubit: The qubit on which the returned Operation operates
                on.

        Returns:
            The operation that operates on the qubit for that moment.
        """
        if self.operates_on([qubit]):
            return self.__getitem__(qubit)
        return None
Returns the operation on a certain qubit for the moment.

        Args:
            qubit: The qubit on which the returned Operation operates
                on.

        Returns:
            The operation that operates on the qubit for that moment.
        
cirq-core/cirq/circuits/moment.py