code: def add_headers(self, header_dict):
          # type: (Dict[str, str]) -> None
          
          if not self.response:
              return
          for name, data_type in header_dict.items():
              value = self.response.headers.get(name)
              value = self._deserialize(data_type, value)
              self.headers[name] = value
docs: Deserialize a specific header.
  
          :param dict header_dict: A dictionary containing the name of the
           header and the type to deserialize to.