app/Dorcas/Utilities/Mailchimp/Mailchimp.php
/**
     * Maintains a singleton instance of the class
     *
     * @param array $config
     *
     * @return Mailchimp
     */
Maintains a singleton instance of the class
@param array $config

@return Mailchimp
Maintains a singleton instance of the class @param array $config @return Mailchimp
public static function instance(array $config = []): Mailchimp
    {
        if (self::$instance === null) {
            self::$instance = new static($config);
        }
        return self::$instance;
    }
public static function instance ( array $ config = [ ] ) : Mailchimp { if ( self :: $ instance === null ) { self :: $ instance = new static ( $ config ) ; } return self :: $ instance ; }
Maintains a singleton instance of the class
 @param array $config
Maintains a singleton instance of the class @param array $config