docs: function isRequired(param, value) {
    if (_.isUndefined(value) || _.isNull(value) || value === '') {
      var isParamRequired = param.required && !param.defaultValue;
      return isParamRequired
        ? errorReturn("%s is required", param.name)
        : successReturn(param.hasOwnProperty('defaultValue') ? param.defaultValue : value);
    }
  }