@NotNull
  InspectionSeverityGroupNode createSeverityGroupNode(SeverityRegistrar severityRegistrar,
                                                      HighlightDisplayLevel level,
                                                      @NotNull InspectionTreeNode parent) {
    return getOrAdd(level, parent, () -> new InspectionSeverityGroupNode(severityRegistrar, level, parent));
  }
@NotNull
  InspectionSeverityGroupNode createSeverityGroupNode(SeverityRegistrar severityRegistrar,
                                                      HighlightDisplayLevel level,
                                                      @NotNull InspectionTreeNode parent)