Cleans up comments/naming regarding TrimTree

internal/graph/graph.go

 // report entries with the same info.
 type NodeMap map[NodeInfo]*Node
 
-// NodeSet maps is a collection of node info structs.
+// NodeSet is a collection of node info structs.
 type NodeSet map[NodeInfo]bool
 
-type nodePtrSet map[*Node]bool
+// NodePtrSet is a collection of Nodes. Trimming a graph or tree requires a set
+// of objects that uniquely identify which nodes to keep. In a graph, NodeInfo
+// works as a unique identifier; however, in a tree, multiple nodes may share
+// identical NodeInfos. *Node do uniquely identify nodes so we can use those
+// instead.Though *Node also uniquely identify nodes in a Graph, we currently
+// rebuild Graphs from scratch using only the NodeSet when trimming, so there
+// would not be the required context of the initial graph to allow for the use
+// of *Node to identify the nodes.
+type NodePtrSet map[*Node]bool
 
 // FindOrInsertNode takes the info for a node and either returns a matching node
 // from the node map if one exists, or adds one to the map if one does not.
 
 // 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 nodePtrSet) {
+func (g *Graph) TrimTree(kept NodePtrSet) {
 	// Creates a new list of nodes
 	oldNodes := g.Nodes
 	g.Nodes = make(Nodes, 0, len(kept))
 
 // discardLowFrequencyNodePtrs returns a NodePtrSet of nodes at or over a
 // specific cum value cutoff.
-func (g *Graph) DiscardLowFrequencyNodePtrs(nodeCutoff int64) nodePtrSet {
-	cutNodes := getNodesWithCumCutoff(g.Nodes, nodeCutoff)
-	kept := make(nodePtrSet, len(cutNodes))
+func (g *Graph) DiscardLowFrequencyNodePtrs(nodeCutoff int64) NodePtrSet {
+	cutNodes := getNodesAboveCumCutoff(g.Nodes, nodeCutoff)
+	kept := make(NodePtrSet, len(cutNodes))
 	for _, n := range cutNodes {
 		kept[n] = true
 	}
 }
 
 func makeNodeSet(nodes Nodes, nodeCutoff int64) NodeSet {
-	cutNodes := getNodesWithCumCutoff(nodes, nodeCutoff)
+	cutNodes := getNodesAboveCumCutoff(nodes, nodeCutoff)
 	kept := make(NodeSet, len(cutNodes))
 	for _, n := range cutNodes {
 		kept[n.Info] = true
 	return kept
 }
 
-// Returns all the nodes who have a Cum value greater than or equal to cutoff
-func getNodesWithCumCutoff(nodes Nodes, nodeCutoff int64) Nodes {
+// getNodesAboveCumCutoff returns all the nodes who have a Cum value greater
+// than or equal to cutoff
+func getNodesAboveCumCutoff(nodes Nodes, nodeCutoff int64) Nodes {
 	cutoffNodes := make(Nodes, 0, len(nodes))
 	for _, n := range nodes {
 		if abs64(n.Cum) < nodeCutoff {
 	}
 }
 
-// selectTopNodePtrs returns a set of the top maxNodes *Node in a graph.
-func (g *Graph) SelectTopNodePtrs(maxNodes int, visualMode bool) nodePtrSet {
-	set := make(nodePtrSet)
+// SelectTopNodePtrs returns a set of the top maxNodes *Node in a graph.
+func (g *Graph) SelectTopNodePtrs(maxNodes int, visualMode bool) NodePtrSet {
+	set := make(NodePtrSet)
 	for _, node := range g.selectTopNodes(maxNodes, visualMode) {
 		set[node] = true
 	}

internal/graph/graph_test.go

 type TrimTreeTestCase struct {
 	Initial  *Graph
 	Expected []ExpectedNode
-	Keep     nodePtrSet
+	Keep     NodePtrSet
 }
 
 // Makes the edge from parent to child residual
 }
 
 // Creates an array of ExpectedNodes from nodes.
-func createExpectedNodes(nodes ...*Node) ([]ExpectedNode, nodePtrSet) {
+func createExpectedNodes(nodes ...*Node) ([]ExpectedNode, NodePtrSet) {
 	Expected := make([]ExpectedNode, len(nodes))
-	Keep := make(nodePtrSet, len(nodes))
+	Keep := make(NodePtrSet, len(nodes))
 
 	for i, node := range nodes {
 		Expected[i] = ExpectedNode{