Source: templates/single-course/lessons.php

<?php
/**
 * The Template for displaying all single course meta information.
 *
 * Override this template by copying it to yourtheme/sensei/single-course/course-lessons.php
 *
 * @author      Automattic
 * @package     Sensei
 * @category    Templates
 * @version     1.9.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}
?>

<section class="course-lessons">

	<?php

		/**
		 * Actions just before the sensei single course lessons loop begins
		 *
		 * @since 1.9.0
		 *
		 * @hook sensei_single_course_lessons_before
		 *
		 * @hooked Sensei_Course::load_single_course_lessons_query
		 */
		do_action( 'sensei_single_course_lessons_before' );

	?>

	<?php

	// lessons loaded into loop in the sensei_single_course_lessons_before hook
	if ( have_posts() ) :

		// start course lessons loop
		while ( have_posts() ) :
			the_post();
			?>

			<article <?php post_class(); ?> >

				<?php

					/**
					 * The hook is inside the course lesson on the single course. It fires
					 * for each lesson. It is just before the lesson excerpt.
					 *
					 * @since 1.9.0
					 *
					 * @hook sensei_single_course_inside_before_lesson
					 *
					 * @param {int} $lessons_id Lesson ID.
					 *
					 * @hooked Sensei_Lesson::the_lesson_meta -  5
					 * @hooked Sensei_Lesson::the_lesson_thumbnail - 8
					 */
					do_action( 'sensei_single_course_inside_before_lesson', get_the_ID() );

				?>

				<section class="entry">

					<?php
					/**
					 * Display the lesson excerpt
					 */
					the_excerpt();
					?>

				</section>

				<?php

					/**
					 * The hook is inside the course lesson on the single course. It is just before the lesson closing markup.
					 * It fires for each lesson.
					 *
					 * @since 1.9.0
					 *
					 * @hook sensei_single_course_inside_after_lesson
					 *
					 * @param {int} $lessons_id The lesson ID.
					 */
					do_action( 'sensei_single_course_inside_after_lesson', get_the_ID() );

				?>

			</article>

		<?php endwhile; ?>

	<?php endif; ?>

	<?php

		/**
		 * Actions just before the sensei single course lessons loop begins
		 *
		 * @hooked Sensei_Course::reset_single_course_query
		 *
		 * @since 1.9.0
		 *
		 * @hook sensei_single_course_lessons_after
		 */
		do_action( 'sensei_single_course_lessons_after' );

	?>

</section>