telemetry ({ api }, { onError, onCompleted } = {}) {
    const observer = new TelemetryObserver({ onCompleted, onError })

    this.write(RequestMessage.telemetry({ api }), observer, false)

    return observer
  }
Send a TELEMETRY through the underlying connection.

@param {object} param0 Message params
@param {number} param0.api The API called
@param {object} param1 Configuration and callbacks callbacks
@param {function()} param1.onCompleted Called when completed
@param {function()} param1.onError Called when error
@return {StreamObserver} the stream observer that monitors the corresponding server response.