Custom H1 for CMB2

customh1-cmb2.php

<?php
function nest_custom_title( $post_id = 0, $before = '', $after = '', $echo = true ) {
	if ( 0 == $post_id ) {
		$post_id = get_the_ID();
	}
	ob_start();
	echo $before;
    $title = get_post_meta( $post_id, '_custom_h1', true );
    if ( false == $title || empty( $title ) ) {
		echo esc_html( get_the_title( $post_id ) );	    
    } else {
	    echo esc_html( $title ); 
    }
    echo $after;
    $title = ob_get_clean();
    if ( $echo ) {
	    echo $title;
    } else {
	    return $title;
    }
}
?>