def _measurement_key_name_(self) -> str:
        """Return the string key that will be used to identify this measurement.

        When a measurement occurs, either on hardware, or in a simulation,
        this is the key value under which the results of the measurement
        will be stored.
        """
Return the string key that will be used to identify this measurement.

        When a measurement occurs, either on hardware, or in a simulation,
        this is the key value under which the results of the measurement
        will be stored.
        
cirq-core/cirq/protocols/measurement_key_protocol.py