code: def to_header(self):
          
          d = dict(self)
          auth_type = d.pop("__auth_type__", None) or "basic"
          return "%s %s" % (
              auth_type.title(),
              ", ".join(
                  [
                      "%s=%s"
                      % (
                          key,
                          quote_header_value(
                              value, allow_token=key not in self._require_quoting
                          ),
                      )
                      for key, value in iteritems(d)
                  ]
              ),
          )
docs: Convert the stored values into a WWW-Authenticate header.