def is_in(self, w, mapping):
        r"""
        It's kind of difficult to decide if something might be a keyword
        in VimL because it allows you to abbreviate them.  In fact,
        'ab[breviate]' is a good example.  :ab, :abbre, or :abbreviate are
        valid ways to call it so rather than making really awful regexps
        like::

            \bab(?:b(?:r(?:e(?:v(?:i(?:a(?:t(?:e)?)?)?)?)?)?)?)?\b

        we match `\b\w+\b` and then call is_in() on those tokens.  See
        `scripts/get_vimkw.py` for how the lists are extracted.
        """
        p = bisect(mapping, (w,))
        if p > 0:
            if mapping[p-1][0] == w[:len(mapping[p-1][0])] and \
               mapping[p-1][1][:len(w)] == w:
                return True
        if p < len(mapping):
            return mapping[p][0] == w[:len(mapping[p][0])] and \
                mapping[p][1][:len(w)] == w
        return False
r"""
        It's kind of difficult to decide if something might be a keyword
        in VimL because it allows you to abbreviate them.  In fact,
        'ab[breviate]' is a good example.  :ab, :abbre, or :abbreviate are
        valid ways to call it so rather than making really awful regexps
        like::

            \bab(?:b(?:r(?:e(?:v(?:i(?:a(?:t(?:e)?)?)?)?)?)?)?)?\b

        we match `\b\w+\b` and then call is_in() on those tokens.  See
        `scripts/get_vimkw.py` for how the lists are extracted.