Gets sorted style titles keyed by their names belonging to the given group.
If an empty string is given, returns all styles.
string $group: (optional) The style group. Defaults to empty string.
bool $access_check: (optional) Whether we should check the style access. Defaults to false.
array An array of style titles keyed by the respective style machine names.
public function getStyleOptions($group = '', $access_check = FALSE);