public static function activate_keys( $keys, $force = false ) {

		// Sanitize before sending.
		if ( ! is_array( $keys ) ) {
			$keys = explode( PHP_EOL, $keys );
		}

		$keys = array_map( 'sanitize_text_field', $keys );
		$keys = array_map( 'trim', $keys );
		$keys = array_unique( $keys );
		$keys = array_filter( $keys ); // Remove empty keys.

		$data = array(
			'keys' => $keys,
			'url'  => get_site_url(),
		);

		// Check for a cached result based on the keys and url input.
		$cache_hash = md5( wp_json_encode( $data ) );
		if ( $force ) {
			// Delete cache if forcing a remote check.
			delete_site_transient( 'llms_helper_keys_activation_response_' . $cache_hash );
		} else {
			// Use the cached result if present.
			$cached_req_result = get_site_transient( 'llms_helper_keys_activation_response_' . $cache_hash );
			if ( ! empty( $cached_req_result ) ) {
				return $cached_req_result;
			}
		}

		$req = new LLMS_Dot_Com_API( '/license/activate', $data );
		set_site_transient( 'llms_helper_keys_activation_response_' . $cache_hash, $req->get_result(), HOUR_IN_SECONDS );

		return $req->get_result();
	}