code: def _compress_json(self, j):
          
          compressed_json = copy.copy(j)
          compressed_json.pop('users', None)
  
          compressed_data = zlib.compress(
              json.dumps(j['users']).encode('utf-8'),
              self.zlib_compression_strength
          )
          b64_data = base64.b64encode(compressed_data).decode('utf-8')
  
          compressed_json['blob'] = b64_data
  
          return compressed_json
docs: Compress the BLOB data portion of the usernotes.
  
          Arguments:
              j: the JSON in Schema v5 format (dict)
  
          Returns a dict with the 'users' key removed and 'blob' key added