public function add_gateways( $methods ) {
	$methods[$this->priority] =
		array(
			'label'           => __( 'Sample', 'wpjobster-sample' ),
			'action'          => '',
			'unique_id'       => $this->unique_slug,
			'process_action'  => 'wpjobster_taketo_sample_gateway',
			'response_action' => 'wpjobster_processafter_sample_gateway',
		);
	add_action( 'wpjobster_show_paymentgateway_forms', 
			array( $this, 'show_gateways' ), $this->priority, 3 );

	return $methods;
}

This function links the settings, checkout and processing functions to the actions from the constructor.