verify_return_to (OpenID::TrustRoot)

    # File lib/openid/trustroot.rb, line 113
        def TrustRoot.verify_return_to(realm_str, return_to, _vrfy=nil)
          # _vrfy parameter is there to make testing easier
          if _vrfy.nil?
            _vrfy = self.method('get_allowed_return_urls')
          end

          if !(_vrfy.is_a?(Proc) or _vrfy.is_a?(Method))
            raise ArgumentError, "_vrfy must be a Proc or Method"
          end

          realm = TrustRoot.parse(realm_str)
          if realm.nil?
            # The realm does not parse as a URL pattern
            return false
          end

          begin
            allowable_urls = _vrfy.call(realm.build_discovery_url())
          rescue RealmVerificationRedirected => err
            Util.log(err.to_s)
            return false
          end

          if return_to_matches(allowable_urls, return_to)
            return true
          else
            Util.log("Failed to validate return_to #{return_to} for " +
                "realm #{realm_str}, was not in #{allowable_urls}")
            return false
          end
        end