code: public final Iterator<AbstractTraceRegion> leafIterator() {
  		if (nestedRegions == null)
  			return Collections.<AbstractTraceRegion> singleton(this).iterator();
  		return new LeafIterator(this);
  	}
docs: Returns an iterator that will only offer leaf trace regions. If the nested regions have gaps, these will be
  filled with parent data. If this region is a leaf, a singleton iterator will be returned.
  
  @return an unmodifiable iterator for all leafs. Never <code>null</code>.