This gist is used in the tutorial https://www.vijayan.in/how-to-create-custom-table-list-in-wordpress-admin-page

human_readable.php

<?php
...

	/**
	 * Convert slug string to human readable.
	 *
	 * @param string $title String to transform human readable.
	 *
	 * @return string Human readable of the input string.
	 */
	private function human_readable( $title ) {
		return ucwords( str_replace( '_', ' ', $title ) );
	}
...