What is a Full Stack Developer: Required Skills and Responsibilities

Fatal error: Uncaught Error: Call to undefined function ajipro_posted_on() in /var/www/html/wordpress/wp-content/themes/ajipro/template-parts/content.php:25 Stack trace: #0 /var/www/html/wordpress/wp-includes/template.php(772): require() #1 /var/www/html/wordpress/wp-includes/template.php(716): load_template('/var/www/html/w...', false, Array) #2 /var/www/html/wordpress/wp-includes/general-template.php(204): locate_template(Array, true, false, Array) #3 /var/www/html/wordpress/wp-content/themes/ajipro/single.php(19): get_template_part('template-parts/...', 'post') #4 /var/www/html/wordpress/wp-includes/template-loader.php(106): include('/var/www/html/w...') #5 /var/www/html/wordpress/wp-blog-header.php(19): require_once('/var/www/html/w...') #6 /var/www/html/wordpress/index.php(17): require('/var/www/html/w...') #7 {main} thrown in /var/www/html/wordpress/wp-content/themes/ajipro/template-parts/content.php on line 25