Sensei - Check if a lesson has a quiz

function.php

<?php
/**
 * Check if a lesson contains a quiz
 * 
 * @param  integer $lesson_id ID of lesson
 * @return boolean            True if lesson contains a quiz, false if not
 */ 
if( ! function_exists( 'sensei_lesson_has_quiz' ) ) {
  function sensei_lesson_has_quiz( $lesson_id = 0 ) {

    if( $lesson_id ) {

      $has_quiz = get_post_meta( $lesson_id, '_quiz_has_questions', true );

      if( $has_quiz ) {
        return true;
      }

    }

    return false;
  }
}
?>