code: int getHalfEdgeUserIndex(int half_edge, int index) {
  		int i = getHalfEdgeIndex_(half_edge);
  		AttributeStreamOfInt32 stream = m_edgeIndices.get(index);
  		if (stream.size() <= i)
  			return -1;
  
  		return stream.read(i);
  	}
docs: Returns a user index value for the half edge