docs: function (binding, subpath, compare) {
        var args = Util.resolveArgs(
          arguments,
          'binding', function (x) { return Util.canRepresentSubpath(x) ? 'subpath' : null; }, '?compare'
        );
  
        return args.binding.sub(args.subpath).isChanged(this._previousState, args.compare || Imm.is);
      }