code: public static <T> StreamObserver<T> asyncUnimplementedStreamingCall(
        MethodDescriptor<?, ?> methodDescriptor, StreamObserver<?> responseObserver) {
      // NB: For streaming call we want to do the same as for unary call. Fail-fast by setting error
      // on responseObserver and then return no-op observer.
      asyncUnimplementedUnaryCall(methodDescriptor, responseObserver);
      return new NoopStreamObserver<>();
    }
docs: Sets unimplemented status for streaming call.
  
  @param methodDescriptor of method for which error will be thrown.
  @param responseObserver on which error will be set.