@NotNull
  private static Set<String> getSupportedStringPrefixes(@NotNull LanguageLevel level) {
    if (level.isPython2()) {
      return PYTHON2_PREFIXES;
    }
    else if (level.isOlderThan(LanguageLevel.PYTHON36)) {
      return PYTHON34_PREFIXES;
    }
    else {
      return PYTHON36_PREFIXES;
    }
  }
@NotNull
  private static Set<String> getSupportedStringPrefixes(@NotNull LanguageLevel level)