get current post ID in wpcf7_swv_create_schema hook

Hey, how can I get the current post id within the wpcf7_swv_create_schema hook? I need to limit the checkboxes by an acf number field of the current post. so instead of the first $max = 2; i need it to be the commented out get_field.

add_action('wpcf7_swv_create_schema',function ( $schema, $contact_form ) {
$max = 2;
// $max = get_field('maximum_themen', get_the_ID());
$schema->add_rule(
wpcf7_swv_create_rule( 'maxitems', array(
'field' => 'your-unterkategorien',
'threshold' => $max,
'error' => "Maximum ".$max." Themen",
) )
);
}, 10, 2);