code: def _preparse(source, f=_compose(_replace_locals, _replace_booleans,
                                   _rewrite_assign,
                                   _clean_spaces_backtick_quoted_names)):
      
      assert callable(f), 'f must be callable'
      return tokenize.untokenize(lmap(f, tokenize_string(source)))
docs: Compose a collection of tokenization functions
  
      Parameters
      ----------
      source : str
          A Python source code string
      f : callable
          This takes a tuple of (toknum, tokval) as its argument and returns a
          tuple with the same structure but possibly different elements. Defaults
          to the composition of ``_rewrite_assign``, ``_replace_booleans``, and
          ``_replace_locals``.
  
      Returns
      -------
      s : str
          Valid Python source code
  
      Notes
      -----
      The `f` parameter can be any callable that takes *and* returns input of the
      form ``(toknum, tokval)``, where ``toknum`` is one of the constants from
      the ``tokenize`` module and ``tokval`` is a string.