public static @Nullable @Nls String combineAccessibleStrings(@Nullable @Nls String s1, @Nullable @Nls String s2) {
    return combineAccessibleStrings(s1, " ", s2);
  }
public static @Nullable @Nls String combineAccessibleStrings(@Nullable @Nls String s1, @Nullable @Nls String s2)