Add custom style sheet on new post or edit post admin pages - WordPress

/**
 * is_edit_page 
 * function to check if the current page is a post edit page
 */
function is_edit_page($new_edit = null){
	global $pagenow;
	//make sure we are on the backend
	if (!is_admin()) return false;

	if($new_edit == "edit")
		return in_array( $pagenow, array( 'post.php',  ) );
	elseif($new_edit == "new") //check for new post page
		return in_array( $pagenow, array( 'post-new.php' ) );
	else //check for either new or edit
		return in_array( $pagenow, array( 'post.php', 'post-new.php' ) );
}

/**
 * Adds the meta box stylesheet when appropriate
 */
function add_metabox_admin_style( $hook ) {
   if (is_edit_page()){ 
		wp_enqueue_style( 'prfx_meta_box_styles', get_template_directory_uri() . '/css/meta-box-styles.css' );
   }
}
add_action( 'admin_print_styles', 'add_metabox_admin_style', 10, 1 );