How to use the aurelia-validation.validationMessages.email function in aurelia-validation

setCustomMessages() {
        validationMessages.minLength = this.configuration.messages.minLength || validationMessages.minLength;
        validationMessages.maxLength = this.configuration.messages.maxLength || validationMessages.maxLength;
        validationMessages.matches = this.configuration.messages.pattern || validationMessages.matches;
        validationMessages.email = this.configuration.messages.format_email || validationMessages.email;
    }
    add() {

setCustomMessages() {
    validationMessages.minLength = this.configuration.messages.minLength || validationMessages.minLength;
    validationMessages.maxLength = this.configuration.messages.maxLength || validationMessages.maxLength;
    validationMessages.matches = this.configuration.messages.pattern || validationMessages.matches;
    validationMessages.email = this.configuration.messages.format_email || validationMessages.email;
  }