docs: def pre_freeze_hook(self):
          """Pre :meth:`dtoolcore.ProtoDataSet.freeze` actions.
  
          This method is called at the beginning of the
          :meth:`dtoolcore.ProtoDataSet.freeze` method.
  
          It may be useful for remote storage backends to generate
          caches to remove repetitive time consuming calls
          """
          allowed = set([v[0] for v in _STRUCTURE_PARAMETERS.values()])
          for d in os.listdir(self._abspath):
              if d not in allowed:
                  msg = "Rogue content in base of dataset: {}".format(d)
                  raise(DiskStorageBrokerValidationWarning(msg))