code: def add_tcp_flag(self, tcp_flag):
          
  
          if tcp_flag not in [1, 2, 4, 8, 16, 32, 64, 128]:
              raise ValueError("Invalid TCP flag. Valid: [1, 2, 4, 8, 16,32, 64, 128]")
  
          prev_size = 0
  
          if self._json_dict.get('tcp_flags') is None:
              self._json_dict['tcp_flags'] = 0
          else:
              prev_size = len(str(self._json_dict['tcp_flags'])) + len('tcp_flags') + 3  # str, key, key quotes, colon
          self._json_dict['tcp_flags'] |= tcp_flag
  
          # update size
          new_size = len(str(self._json_dict['tcp_flags'])) + len('tcp_flags') + 3  # str, key, key quotes, colon
          self._size += new_size - prev_size
  
          if prev_size == 0 and self._has_field:
              # add the comma and space
              self._size += 2
          self._has_field = True
docs: Add a single TCP flag - will be OR'd into the existing bitmask