one of "dwn_mtx", an adjacency matrix for a downstream directed SBN, "up_mtx", an adjacency matrix for a upstream directed SBN, "undir_mtx", an adjacency matrix for a undirected SBN, "n2n_dist_up", "n2n_dist_dwn" or "n2n_dist_undir", an adjacency matrix of upstream, downstream or undirected node to node distances.