private @Nullable AbstractBlockWrapper getPrevIndentedSiblingFast(final @NotNull AbstractBlockWrapper current) {
    if (myPrevBlockCalculator == null) {
      myPrevBlockCalculator = new ProbablyIncreasingLowerboundAlgorithm<>(myChildren);
    }

    final List<AbstractBlockWrapper> leftBlocks = myPrevBlockCalculator.getLeftSubList(current);
    for (int i = leftBlocks.size() - 1; i >= 0; i--) {
      final AbstractBlockWrapper child = leftBlocks.get(i);
      if (child.getWhiteSpace().containsLineFeeds()) {
        return child;
      }
    }
    return null;
  }
private @Nullable AbstractBlockWrapper getPrevIndentedSiblingFast(final @NotNull AbstractBlockWrapper current)