Source

File: wp-includes/class-wp-theme.php

public function __isset( $offset ) {
		static $properties = array(
			'name',
			'title',
			'version',
			'parent_theme',
			'template_dir',
			'stylesheet_dir',
			'template',
			'stylesheet',
			'screenshot',
			'description',
			'author',
			'tags',
			'theme_root',
			'theme_root_uri',
		);

		return in_array( $offset, $properties, true );
	}