A ClusterTree is a more general structure than an EliminationTree or JunctionTree. It represents a tree where each node (a ‘Cluster’) contains a subset of factors from an original factor graph. The key property is that the tree must be ‘family preserving’, meaning each original factor must belong entirely within a single cluster.
ClusterTree itself is a base class. EliminatableClusterTree adds the ability to perform elimination, and JunctionTree is a specific type of EliminatableClusterTree derived from an EliminationTree.
Direct use of ClusterTree in Python applications is uncommon; see the subclasses.