An internal vertex of a tree is a vertex that is not a leaf, meaning it has degree at least 2. This function lists such vertices. Each vertex is specified by the partition of the set of leaves formed by removing the vertex. Each partition is given as a List of Sets.

i1 : T = leafTree(4,{{0,1}}); |

i2 : internalVertices T o2 = {{set {0, 1}, set {3}, set {2}}, {set {0}, set {1}, set {2, 3}}} o2 : List |

i3 : #(internalVertices T) o3 = 2 |

- vertices(LeafTree) -- List the vertices of a tree

- internalVertices(LeafTree)