code: function(field, allowedValues) {
      if (Array.isArray(field)) {
        return this.validateFieldsHelper(
          field,
          [allowedValues],
          this.validatesInclusionOf
        )
      }
  
      return this.validates(field, function() {
        var valid = true
        if (this[field]) valid = allowedValues.indexOf(this[field]) !== -1
        if (!valid)
          this.errors.add(
            field,
            'only allow one of [' + allowedValues.join(', ') + ']'
          )
        return valid
      })
    }
docs: This validator checks if the given field`s values is an allowed value
  @class Definition
  @method validatesInclusionOf
  @param {string} field - The field to validate
  @param {array} allowedValues - The array of allowed values
  
  @return {Definition}