docs: def spectrodir(self, filetype, **kwargs):
          """Returns :envvar:`SPECTRO_REDUX` or :envvar:`BOSS_SPECTRO_REDUX`
          depending on the value of `run2d`.
  
          Parameters
          ----------
          filetype : str
              File type parameter.
          run2d : int or str
              2D Reduction ID.
  
          Returns
          -------
          spectrodir : str
              Value of the appropriate environment variable.
          """
          if str(kwargs['run2d']) in ('26', '103', '104'):
              return os.environ['SPECTRO_REDUX']
          else:
              return os.environ['BOSS_SPECTRO_REDUX']