_fix_ns (OpenID::Message)

    # File lib/openid/message.rb, line 305
        def _fix_ns(namespace)
          if namespace == OPENID_NS
            unless @openid_ns_uri
              raise UndefinedOpenIDNamespace, 'OpenID namespace not set'
            else
              namespace = @openid_ns_uri
            end
          end

          if namespace == BARE_NS
            return namespace
          end

          if !namespace.is_a?(String)
            raise ArgumentError, ("Namespace must be BARE_NS, OPENID_NS or "\
                                  "a string. Got #{namespace.inspect}")
          end

          if namespace.index(':').nil?
            msg = ("OpenID 2.0 namespace identifiers SHOULD be URIs. "\
                   "Got #{namespace.inspect}")
            Util.log(msg)

            if namespace == 'sreg'
              msg = "Using #{SREG_URI} instead of \"sreg\" as namespace"
              Util.log(msg)
              return SREG_URI
            end
          end

          return namespace
        end