code: def postprocess(self, input_dicts, fetch_dict, data_id, log_id):
      out = {"res_mean_val": []}
      results = fetch_dict[self.output_name]
      for val in results:
          val = val.tolist()
          val = np.array(val)
          out["res_mean_val"].append(np.mean(val))
      out["res_mean_val"] = str(out["res_mean_val"])
      return out, None, ""
  
imports: import io
  import os
  import sys
  import base64
  import argparse
  import yaml
  import numpy
  from PIL import Image
  from paddle_serving_server.web_service import WebService, Op
  from preprocess_ops import ResizeImage, CenterCropImage, NormalizeImage, ToCHW, Compose
label_desc: Use image node_id 4 for calling the SegOp obj's underlying member method code with example usage: obj.postprocess(input_dicts, fetch_dict, data_id, log_id) and returns: out,  None,  str