'Returns the previous token relative to *idx*.
If *skip_ws* is ``True`` (the default) whitespace tokens are ignored.
If *skip_cm* is ``True`` comments are ignored.
``None`` is returned if there\'s no previous token.'

def token_prev(self, idx, skip_ws=True, skip_cm=False):

    return self.token_next(idx, skip_ws, skip_cm, _reverse=True)
