return strings.Join(matches[1:], "")
		}
	}
	return f
}

// TrimTree trims a Graph in forest form, keeping only the nodes in kept. This
// will not work correctly if even a single node has multiple parents.
func (g *Graph) TrimTree(kept NodePtrSet) {
	// Creates a new list of nodes
	oldNodes := g.Nodes
	g.Nodes = make(Nodes, 0, len(kept))

	if nodeCutoff > 0 {
		if callTree {
			if nodesKept := g.DiscardLowFrequencyNodePtrs(nodeCutoff); len(g.Nodes) != len(nodesKept) {
				droppedNodes = len(g.Nodes) - len(nodesKept)
				g.TrimTree(nodesKept)
			}
		} else {
			if nodesKept := g.DiscardLowFrequencyNodes(nodeCutoff); len(g.Nodes) != len(nodesKept) {
				droppedNodes = len(g.Nodes) - len(nodesKept)
				g = rpt.newGraph(nodesKept)
			}
		}