GCloud MLEngine:Create Version failed. Bad model detected with error: Failed to load model: a bytes-like object is required, not 'str' (Error code: 0) - tensorflow

Question

I am trying to create version under google cloud ml models for the successfully trained tensorflow estimator model. I believe that I am providing the correct Uri(in google storage) which includes saved_model.pb.
Framework: Tensorflow,
Framework Version: 1.13.1,
Runtime Version: 1.13,
Python: 3.5
Here is the traceback of the error:
Traceback (most recent call last):
File "/google/google-cloud-sdk/lib/googlecloudsdk/calliope/cli.py", line 985, in Execute
resources = calliope_command.Run(cli=self, args=args)
File "/google/google-cloud-sdk/lib/googlecloudsdk/calliope/backend.py", line 795, in Run
resources = command_instance.Run(args)
File "/google/google-cloud-sdk/lib/surface/ml_engine/versions/create.py", line 119, in Run
python_version=args.python_version)
File "/google/google-cloud-sdk/lib/googlecloudsdk/command_lib/ml_engine/versions_util.py", line 114, in Create
message='Creating version (this might take a few minutes)...')
File "/google/google-cloud-sdk/lib/googlecloudsdk/command_lib/ml_engine/versions_util.py", line 75, in WaitForOpMaybe
return operations_client.WaitForOperation(op, message=message).response
File "/google/google-cloud-sdk/lib/googlecloudsdk/api_lib/ml_engine/operations.py", line 114, in WaitForOperation
sleep_ms=5000)
File "/google/google-cloud-sdk/lib/googlecloudsdk/api_lib/util/waiter.py", line 264, in WaitFor
sleep_ms, _StatusUpdate)
File "/google/google-cloud-sdk/lib/googlecloudsdk/api_lib/util/waiter.py", line 326, in PollUntilDone
sleep_ms=sleep_ms)
File "/google/google-cloud-sdk/lib/googlecloudsdk/core/util/retry.py", line 229, in RetryOnResult
if not should_retry(result, state):
File "/google/google-cloud-sdk/lib/googlecloudsdk/api_lib/util/waiter.py", line 320, in _IsNotDone
return not poller.IsDone(operation)
File "/google/google-cloud-sdk/lib/googlecloudsdk/api_lib/util/waiter.py", line 122, in IsDone
raise OperationError(operation.error.message)
OperationError: Bad model detected with error: "Failed to load model: a bytes-like object is required, not 'str' (Error code: 0)"
ERROR: (gcloud.ml-engine.versions.create) Bad model detected with error: "Failed to load model: a bytes-like object is required, not 'str' (Error code: 0)"
Do you have any idea what might be the problem?
EDIT
I am using:
tf.estimator.LatestExporter('exporter', model.serving_input_fn)
as a estimator exporter.
serving_input_fn:
def serving_input_fn():
inputs = {'string1': tf.placeholder(tf.int16, [None, MAX_SEQUENCE_LENGTH]),
'string2': tf.placeholder(tf.int16, [None, MAX_SEQUENCE_LENGTH])}
return tf.estimator.export.ServingInputReceiver(inputs, inputs)
PS: my model takes two inputs and returns one binary output.