private void cleanupBackDependency(final int className, @Nullable Iterable<? extends UsageRepr.Usage> usages, final IntIntMultiMaplet buffer) {
    if (usages == null) {
      usages = Iterators.flat(Iterators.map(getReprsByName(className, ClassFileRepr.class), repr -> repr.getUsages()));
    }
    for (Integer owner : Iterators.unique(Iterators.map(usages, usage -> usage.getOwner()))) {
      if (owner != className) {
        buffer.put(owner, className);
      }
    }
  }
private void cleanupBackDependency(final int className, @Nullable Iterable<? extends UsageRepr.Usage> usages, final IntIntMultiMaplet buffer)