def is_virtual_moment(self, moment: cirq.Moment) -> bool:
        """Returns true iff the given moment is non-empty and all of its
        operations are virtual.

        Moments for which this method returns True should not have additional
        noise applied to them.

        Args:
            moment: ``cirq.Moment`` to check for non-virtual operations.

        Returns:
            True if "moment" is non-empty and all operations in "moment" are
            virtual; false otherwise.
        """
        if not moment.operations:
            return False
        return all(ops.VirtualTag() in op.tags for op in moment)
Returns true iff the given moment is non-empty and all of its
        operations are virtual.

        Moments for which this method returns True should not have additional
        noise applied to them.

        Args:
            moment: ``cirq.Moment`` to check for non-virtual operations.

        Returns:
            True if "moment" is non-empty and all operations in "moment" are
            virtual; false otherwise.
        
cirq-core/cirq/devices/noise_model.py