docs: def body(self):
          """Seralizes and returns the response body.
  
          On subsequent access, returns the cached value."""
          if self._body is None:
              raw_body = self._raw_body
              if self._body_writer is None:
                  self._body = raw_body() if callable(raw_body) else raw_body
              else:
                  self._body = self._body_writer(raw_body)
  
          return self._body