Makes TrimTree have no return type

internal/graph/graph.go

 
 // Trims a Graph that is in forest form to contain only the nodes in kept. This
 // will not work correctly in the case that a node has multiple parents.
-func (g *Graph) TrimTree(kept NodeSet) *Graph {
+func (g *Graph) TrimTree(kept NodeSet) {
 	// Creates a new list of nodes
 	oldNodes := g.Nodes
 	g.Nodes = make(Nodes, 0, len(kept.Ptr))
 		}
 	}
 	g.RemoveRedundantEdges()
-	return g
 }
 
 func joinLabels(s *profile.Sample) string {

internal/report/report.go

 		if nodesKept := g.DiscardLowFrequencyNodes(nodeCutoff); len(g.Nodes) != len(nodesKept.Ptr) {
 			droppedNodes = len(g.Nodes) - len(nodesKept.Ptr)
 			if o.CallTree {
-				g = g.TrimTree(nodesKept)
+				g.TrimTree(nodesKept)
 			} else {
 				g = rpt.newGraph(nodesKept)
 			}
 		g.TrimLowFrequencyEdges(edgeCutoff)
 		if nodesKept := g.SelectTopNodes(nodeCount, visualMode); len(nodesKept.Ptr) != len(g.Nodes) {
 			if o.CallTree {
-				g = g.TrimTree(nodesKept)
+				g.TrimTree(nodesKept)
 			} else {
 				g = rpt.newGraph(nodesKept)
 			}