Normalizes whitespace; called if ``ignore_ws`` is true.

def normalize_whitespace(self, value):
        """Normalizes whitespace; called if ``ignore_ws`` is true."""
        if isinstance(value, unicode):
            return u" ".join(
                x for x in re.split(r'\s+', value, flags=re.UNICODE) if
                len(x)
            )
        else:
            return " ".join(value.split())