/**
     * Class constructor.
     *
     * @since 1.0.0
     */
    public function __construct() {

        $this->_wwp_wholesale_roles = WWP_Wholesale_Roles::getInstance();
        $this->_wwp_custom_fields = WWP_Custom_Fields::getInstance();
        $this->_wwp_wholesale_prices = WWP_Wholesale_Prices::getInstance();

    }
 public static function getInstance()
 {
     if (!self::$_instance instanceof self) {
         self::$_instance = new self();
     }
     return self::$_instance;
 }