code: function newGetOne(endpoint, allowable) {
      var get = newGet(endpoint, allowable);
      return function(id, params, callback) {
          var args = utils.allowOptionalParams(params, callback);
          if (typeof id === "object") {
              _.assign(args.params, id);
          } else {
              args.params.id = id;
          }
  
          return get.call(this, args.params, args.callback);
      };
  }
docs: Return a function for retrieving one item
  
  @param  {Endpoint} endpoint
  @param  {String[]} [allowable]
  @return {itemsGetOneRequest}