docs: @Deprecated
      @RestrictedSince("1.651.2 / 2.TODO")
      @Restricted(NoExternalUse.class)
      public static boolean isAbsoluteUri(@Nonnull String uri) {
          int idx = uri.indexOf(':');
          if (idx<0)  return false;   // no ':'. can't be absolute
  
          // #, ?, and / must not be before ':'
          return idx<_indexOf(uri, '#') && idx<_indexOf(uri,'?') && idx<_indexOf(uri,'/');
      }