docs: def _extract_request_data(self):
          """
          Extracts the data from the representation submitted in the request
          body and returns it.
  
          This default implementation uses a representer for the content type
          specified by the request to perform the extraction and returns an
          object implementing the
          :class:`everest.representers.interfaces.IResourceDataElement`
          interface.
  
          :raises HTTPError: To indicate problems with the request data
            extraction in terms of HTTP codes.
          """
          rpr = self._get_request_representer()
          return rpr.data_from_bytes(self.request.body)