code: def set_default_by_alias(self, alias):
          
          if alias not in self._aliases:
              raise DataInvalidAlias('A dataset with alias {} does not exist'.format(alias))
  
          self._default_index = self._aliases[alias]
docs: Set the default dataset by its alias.
  
          After changing the default dataset, all calls without explicitly specifying the
          dataset by index or alias will be redirected to this dataset.
  
          Args:
              alias (str): The alias of the dataset that should be made the default.
  
          Raises:
              DataInvalidAlias: If the alias does not represent a valid dataset.