docs: def default_aux_file_paths(self, primary_path):
          """
          Get the default paths for auxiliary files relative to the path of the
          primary file, i.e. the same name as the primary path with a different
          extension
  
          Parameters
          ----------
          primary_path : str
              Path to the primary file in the fileset
  
          Returns
          -------
          aux_paths : dict[str, str]
              A dictionary of auxiliary file names and default paths
          """
          return dict((n, primary_path[:-len(self.ext)] + ext)
                      for n, ext in self.aux_files.items())