docs: def _get_raw_data(self, name):
          """Find file holding data and return its content."""
          # try legacy first, then hdf5
          filestem = ''
          for filestem, list_fvar in self._files.items():
              if name in list_fvar:
                  break
          fieldfile = self.step.sdat.filename(filestem, self.step.isnap,
                                              force_legacy=True)
          if not fieldfile.is_file():
              fieldfile = self.step.sdat.filename(filestem, self.step.isnap)
          parsed_data = None
          if fieldfile.is_file():
              parsed_data = stagyyparsers.fields(fieldfile)
          elif self.step.sdat.hdf5 and self._filesh5:
              for filestem, list_fvar in self._filesh5.items():
                  if name in list_fvar:
                      break
              parsed_data = stagyyparsers.read_field_h5(
                  self.step.sdat.hdf5 / 'Data.xmf', filestem, self.step.isnap)
          return list_fvar, parsed_data