class_docstr: GRPCServer test
class_docstr_tok: ["GRPCServer","test"]
code: def test_bytes_io(self):
      test_str = "Hello towhee"
      b = bytes(test_str, "utf-8")
  
      service = api_service.APIService(desc="test")
  
      @service.api(
          path="/echo", input_model=BYTES(), output_model=BYTES()
      )
      def test2(b: bytes):
          assert isinstance(b, bytes)
          s = b.decode("utf-8")
          assert s == test_str
          return bytes("welcome", "utf-8")
  
      self.server = GRPCServer(service)
      self.server.start("localhost", 50001)
  
      with Client("localhost", 50001) as client:
          response = client("/echo", b, BYTES())
          self.assertEqual(b"welcome", response.content)
  
          response = client("/echo", b)
          self.assertEqual(b"welcome", response.content)
  
          with self.assertRaises(AssertionError):
              client("/echo", "error_type", NDARRAY())
  
      async def run_async():
          async with AsyncClient("localhost", 50001) as aclient:
              response = await aclient("/echo", b, BYTES())
              self.assertEqual(b"welcome", response.content)
  
              response = await aclient("/echo", b)
              self.assertEqual(b"welcome", response.content)
  
              with self.assertRaises(AssertionError):
                  await aclient("/echo", "error_type", NDARRAY())
  
      asyncio.run(run_async())
  
imports: import unittest
  import typing
  import asyncio
  from pydantic import BaseModel
  import numpy
  from towhee import api_service, pipe
  from towhee.serve.grpc.server import GRPCServer
  from towhee.serve.grpc.client import Client, AsyncClient
  from towhee.serve.io import JSON, NDARRAY, BYTES
  from towhee.utils.serializer import from_json
label_desc: Use image node_id 9 for calling the TestGRPC obj's underlying member method code with example usage: obj.test_bytes_io() and returns: bytes