Renders the hidden form required for the meta boxes form.

function the_block_editor_meta_box_post_form_hidden_fields( $post ) {
	$form_extra = '';
	if ( 'auto-draft' === $post->post_status ) {
		$form_extra .= "";
	}
	$form_action  = 'editpost';
	$nonce_action = 'update-post_' . $post->ID;
	$form_extra  .= "";
	$referer      = wp_get_referer();
	$current_user = wp_get_current_user();
	$user_id      = $current_user->ID;
	wp_nonce_field( $nonce_action );

	/*
	 * Some meta boxes hook into these actions to add hidden input fields in the classic post form.
	 * For backward compatibility, we can capture the output from these actions,
	 * and extract the hidden input fields.
	 */
	ob_start();
	/** This filter is documented in wp-admin/edit-form-advanced.php */
	do_action( 'edit_form_after_title', $post );
	/** This filter is documented in wp-admin/edit-form-advanced.php */
	do_action( 'edit_form_advanced', $post );
	$classic_output = ob_get_clean();

	$classic_elements = wp_html_split( $classic_output );
	$hidden_inputs    = '';
	foreach ( $classic_elements as $element ) {
		if ( 0 !== strpos( $element, '` fields, which will be POSTed back to
	 * the server when meta boxes are saved.
	 *
	 * @since 5.0.0
	 *
	 * @param WP_Post $post The post that is being edited.
	 */
	do_action( 'block_editor_meta_box_hidden_fields', $post );
}