private void highlightRegExpGroup(int offset, @NotNull PsiFile regExpFile) {
    final RegExpGroup group = findCapturingGroupAtOffset(regExpFile, offset);
    final HighlightManager highlightManager = HighlightManager.getInstance(regExpFile.getProject());
    removeHighlights(highlightManager);
    if (group != null) {
      final int index = SyntaxTraverser.psiTraverser(regExpFile).filter(RegExpGroup.class).indexOf(e -> e == group) + 1;
      highlightRegExpGroup(group, highlightManager);
      highlightMatchGroup(highlightManager, getMatches(regExpFile), index);
    }
    else {
      highlightMatchGroup(highlightManager, getMatches(regExpFile), 0);
    }
  }
private void highlightRegExpGroup(int offset, @NotNull PsiFile regExpFile)