1.2.1 Node ranking
   rank_nodes.py
   rank_nodes_thresh.py
   rank_occurrence.py
  1.2.2 Interlayer degree correlation coefficients
   compute_pearson.py
   compute_rho.py
   compute_tau.py
  1.2.3 Interlayer degree correlation functions
   dump_k_q
   knn_q_from_layers.py
   knn_q_from_degrees.py
   fit_knn