code: def join_json_files(prefix):
      
      try:
          with open(prefix + '.uaz.entities.json', 'rt') as f:
              entities = json.load(f)
          with open(prefix + '.uaz.events.json', 'rt') as f:
              events = json.load(f)
          with open(prefix + '.uaz.sentences.json', 'rt') as f:
              sentences = json.load(f)
      except IOError as e:
          logger.error(
              'Failed to open JSON files for %s; REACH error?' % prefix
              )
          logger.exception(e)
          return None
      return {'events': events, 'entities': entities, 'sentences': sentences}
docs: Join different REACH output JSON files into a single JSON object.
  
      The output of REACH is broken into three files that need to be joined
      before processing. Specifically, there will be three files of the form:
      `<prefix>.uaz.<subcategory>.json`.
  
      Parameters
      ----------
      prefix : str
          The absolute path up to the extensions that reach will add.
  
      Returns
      -------
      json_obj : dict
          The result of joining the files, keyed by the three subcategories.