if len(lines) == 0 {
				lines = []profile.Line{{}} // Create empty line to include location info.
			}
			for lidx := len(lines) - 1; lidx >= 0; lidx-- {
				nodeMap := parentNodeMap[parent]
				if nodeMap == nil {
					nodeMap = make(NodeMap)
					parentNodeMap[parent] = nodeMap
				}
				n := nodeMap.findOrInsertLine(l, lines[lidx], o)
				if n == nil {
					continue
				}