docs: def doc_sub(*sub):
      """
      Decorator for performing substitutions in docstrings.
  
      Using @doc_sub(some_note, other_note) on a function with {0} and {1} in the
      docstring will substitute the contents of some_note and other_note for {0}
      and {1}, respectively.
  
      Decorator appears to work properly both with IPython help (tab completion
      and ?) and with Sphinx.
  
      """
      def dec(obj):
          obj.__doc__ = obj.__doc__.format(*sub)
          return obj
      return dec