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action is not described

get_template_part_(slug) action-hook . WP 3.0.0

Fires before the specified template part file is loaded.

The dynamic portion of the hook name, $slug, refers to the slug name for the generic template part.

Usage

add_action( 'get_template_part_(slug)', 'action_function_name_9664', 10, 2 );
function action_function_name_9664( $slug, $name ){
	// action...
}
$slug(string)
The slug name for the generic template.
$name(string/null)
The name of the specialized template.

Where the hook is called

get_template_part()
get_template_part_(slug)
wp-includes/general-template.php 146
do_action( "get_template_part_{$slug}", $slug, $name );

Where the hook is used (in WP core)

Does not used.