code: function param_adder(path, method, request, request_opts){
    return function(param){
      var value = cust.opt_to_pp(path, method, param.name, request_opts);
      if (F.isExist(value)) {
        var o = {};
        o[param.name] = value;
        request[method === 'GET' ? 'query' : 'send'](o);
      }
    };
  }
docs: Private