Get the parts of the branches leading to a set of nodes or tips
PCMTreeGetPartsForNodes(tree, nodes = seq_len(PCMTreeNumNodes(tree)))
a phylo object with an edge.part member denoting parts.
an integer vector denoting the nodes. Default is seq_len(PCMTreeNumNodes(tree).
a character vector denoting the parts of the branches leading to the nodes, according to tree$edge.part.