Hide admin tool bar from back end dashboard [duplicate]

WordPress page for show_admin_bar says:

You cannot turn off the toolbar on the WordPress dashboard

However, this trick works

    function remove_admin_bar() { ?>
    <style type="text/css">
        body {
            margin-top: -28px;
        }

        body.admin-bar #wphead {
            padding-top: 0;
        }

        #wpadminbar {
            display: none;
        }
    </style>
<?php }

add_action( 'admin_head', 'remove_admin_bar' );

In oreder to remove certain menus from admin bar use $wp_admin_bar->remove_menu($id); where $id of a specific menu can be found in Chrome Dev Tool. Each menus’ <li> id in Dev tool is in the form of wp-admin-bar-{id}, for example Comments menu has id wp-admin-bar-comments. So to remove this menu code should be like this,

// remove links/menus from the admin bar
function my_admin_bar_render() {
    global $wp_admin_bar;
    $wp_admin_bar->remove_menu('comments');
    // Code to remove other items goes here
    ....
    ....
}
add_action( 'wp_before_admin_bar_render', 'my_admin_bar_render' );