code: def test_read_blob(self):
      responses = [
          data_provider_pb2.ReadBlobResponse(data=b"hello wo"),
          data_provider_pb2.ReadBlobResponse(data=b"rld"),
      ]
      self.stub.ReadBlob.return_value = responses
  
      actual = self.provider.read_blob(self.ctx, blob_key="myblob")
      expected = b"hello world"
      self.assertEqual(actual, expected)
  
      req = data_provider_pb2.ReadBlobRequest()
      req.blob_key = "myblob"
      self.stub.ReadBlob.assert_called_once_with(req)
  
imports: from unittest import mock
  import grpc
  import grpc_testing
  import numpy
  from tensorboard import errors
  from tensorboard import test
  from tensorboard import context
  from tensorboard.data import grpc_provider
  from tensorboard.data import provider
  from tensorboard.data.proto import data_provider_pb2
  from tensorboard.data.proto import data_provider_pb2_grpc
  from tensorboard.util import tensor_util
label_desc: Use image node_id 14 for calling the GrpcDataProviderTest obj's underlying member method code with example usage: obj.test_read_blob() without return types