get className() {
    let className = this.hasInput ? `${this.transform('class', 'form-group')} has-feedback `: '';
    className += `formio-component formio-component-${this.component.type} `;
    // TODO: find proper way to avoid overriding of default type-based component styles
    if (this.key && this.key !== 'form') {
      className += `formio-component-${this.key} `;
    }
    if (this.component.multiple) {
      className += 'formio-component-multiple ';
    }
    if (this.component.customClass) {
      className += this.component.customClass;
    }
    if (this.hasInput && this.component.validate && boolValue(this.component.validate.required)) {
      className += ' required';
    }
    if (this.labelIsHidden()) {
      className += ' formio-component-label-hidden';
    }
    if (!this.visible) {
      className += ' formio-hidden';
    }
    return className;
  }
Retrieves the CSS class name of this component.
@returns {string} - The class name of this component.