问 带有迭代器请求的gRPC python上的数据流，但得到“异常迭代请求！”

service ABC {
    rpc DataTransmission (stream DataTransmissionRequest) returns (stream DataTransmissionResponse);
message DataTransmissionRequest {
    bytes data = 1;
    string ticket = 2;
message DataTransmissionResponse {
    bytes data = 1;
}

def generateRequests():
        req_msgs = [
            (b"123", "sySJZDV9Rb8dyqt1"),
            (b"123"),
            (b"123"),
            (b"123"),
            (b"123"),
            (b"123"),
        iter = 0
        for (req, ticket) in req_msgs:
            print("(req, ticket) = ", (req, ticket))
            if iter == 0:
                request = ABC_pb2.DataTransmissionRequest(data=req, ticket=ticket)
            else:
                request = ABC_pb2.DataTransmissionRequest(data=req)
            iter += 1
            print("iter = ", iter)
            yield request
    #my_queue = queue.SimpleQueue()
    with grpc.insecure_channel(addr) as channel:
        stub = ABC_pb2_grpc.ServiceProxyStub(channel)
        data_transmission_resp = stub.DataTransmission(generateRequests())
        print("data_transmission_resp = ", data_transmission_resp)
        ##print("data_transmission_resp = ", list(data_transmission_resp))
        ## use the results
        for data_trans in data_transmission_resp:
            print(data_trans)

grpc._channel._MultiThreadedRendezvous: <_MultiThreadedRendezvous of RPC that terminated with:
        status = StatusCode.UNKNOWN
        details = "Exception iterating requests!"