class_docstr: Implementation. Captures batches in JSON format, returns
  also in JSON format.
code: def format_output(self, data):
      return self._batch_to_json(data, self._lengths)
  
file_path: serve/ts/torch_handler/request_envelope/json.py
imports: import json
  from base64 import b64decode
  from itertools import chain
  from .base import BaseEnvelope
label_desc: Use image node_id 2 for calling the JSONEnvelope obj's underlying member method code with example usage: obj.format_output(data) and returns: self