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.

def _preparse(source, f=_compose(_replace_locals, _replace_booleans,
                                 _rewrite_assign,
                                 _clean_spaces_backtick_quoted_names)):
    """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.
    """
    assert callable(f), 'f must be callable'
    return tokenize.untokenize(lmap(f, tokenize_string(source)))