docs: static String getBuiltInBindingsKey(String key) {
      int start = startOfType(key);
      if (substringStartsWith(key, start, PROVIDER_PREFIX)) {
        return extractKey(key, start, key.substring(0, start), PROVIDER_PREFIX);
      } else if (substringStartsWith(key, start, MEMBERS_INJECTOR_PREFIX)) {
        return extractKey(key, start, "members/", MEMBERS_INJECTOR_PREFIX);
      } else {
        return null;
      }
    }