WordPress at a glance
function is not described

block_version() WP 5.0.0

Returns the current version of the block format that the content string is using.

If the string doesn't contain blocks, it returns 0.

No Hooks.

Return

Int. The block format version is 1 if the content contains one or more blocks, 0 otherwise.

Usage

block_version( $content );
$content(string) (required)
Content to test.

Code of block version: wp-includes/blocks.php WP 5.2.2

<?php
function block_version( $content ) {
	return has_blocks( $content ) ? 1 : 0;
}