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action is not described

pre_get_terms action-hook . WP 4.6.0

Fires before terms are retrieved.

Usage

add_action( 'pre_get_terms', 'action_function_name_5044' );
function action_function_name_5044( $this ){
	// action...
}
$this(WP_Term_Query)
Current instance of WP_Term_Query.

Where the hook is called

WP_Term_Query::get_terms()
wp-includes/class-wp-term-query.php 317
do_action( 'pre_get_terms', $this );

Where the hook is used (in WP core)

Does not used.