Given a minified location, this tries to locate the closest
        token that is a match.  Returns `None` if no match can be found.

def lookup_token(self, line, col):
        """Given a minified location, this tries to locate the closest
        token that is a match.  Returns `None` if no match can be found.
        """
        # Silently ignore underflows
        if line < 0 or col < 0:
            return None
        tok_out = _ffi.new('lsm_token_t *')
        if rustcall(_lib.lsm_view_lookup_token, self._get_ptr(),
                    line, col, tok_out):
            return convert_token(tok_out[0])