code: function (key) {
              var keys = Array.isArray(key) ? key : arguments;
  
              for (var i = 0; i < keys.length; i++) {
                  if (isEmptyString(keys[i])) return false;
              }
  
              return true;
          }
docs: Determine if the request contains a non-empty value for an input item.
  
  @param  {String|Array}  key
  @return bool