Source

File: wp-includes/class-wp-customize-widgets.php

protected function get_captured_option( $option_name, $default = false ) {
		if ( array_key_exists( $option_name, $this->_captured_options ) ) {
			$value = $this->_captured_options[ $option_name ];
		} else {
			$value = $default;
		}
		return $value;
	}