docs: 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())