code: def node_statistics(docgraph):
      
      print "Node statistics\n==============="
      layer_counts = Counter()
      attrib_counts = Counter()
      for node_id, node_attrs in docgraph.nodes_iter(data=True):
          for layer in node_attrs['layers']:
              layer_counts[layer] += 1
          for attrib in node_attrs:
              attrib_counts[attrib] += 1
  
      print "\nnumber of nodes with layers"
      print_sorted_counter(layer_counts)
      print "\nnumber of nodes with attributes"
      print_sorted_counter(attrib_counts)
docs: print basic statistics about a node, e.g. layer/attribute counts