public function add_columns( $columns ) {

		$columns = array(
			'cb'      => '<input type="checkbox" />',
			'title'   => __( 'Lesson Title', 'lifterlms' ),
			'course'  => __( 'Course', 'lifterlms' ),
			'section' => __( 'Section', 'lifterlms' ),
			'prereq'  => __( 'Prerequisite', 'lifterlms' ),
			'author'  => __( 'Author', 'lifterlms' ),
			'date'    => __( 'Date', 'lifterlms' ),
		);

		return $columns;
	}