private void registerChildSpacing(@Nullable Block block1, @NotNull Block block2, Spacing spacing) {
    if (myChildDataBorderSpacings == null) {
      myChildDataBorderSpacings = new HashMap<>();
    }
    myChildDataBorderSpacings.put(new Pair<>(block1, block2), spacing);
  }
private void registerChildSpacing(@Nullable Block block1, @NotNull Block block2, Spacing spacing)