private void removeUsagesInElement(ProjectStructureElement element) {
    final Collection<ProjectStructureElementUsage> usages = myContainingElement2Usages.removeAll(element);
    if (usages != null) {
      for (ProjectStructureElementUsage usage : usages) {
        mySourceElement2Usages.remove(usage.getSourceElement(), usage);
      }
    }
  }
private void removeUsagesInElement(ProjectStructureElement element)