public function getServiceTypes($group = null)
    {
        ksort($this->types, SORT_NATURAL); // sort by name for display
        if (!empty($group)) {
            if (!empty($group) && !is_array($group)) {
                $group = array_map('trim', explode(',', trim($group, ',')));
            }
            $group = array_map('strtolower', (array)$group);
            $types = [];
            foreach ($this->types as $type) {
                if (in_array(strtolower($type->getGroup()), $group)) {
                    $types[$type->getName()] = $type;
                }
            }

            return $types;
        }

        return $this->types;
    }