code: def format_node(import_graph, node, indent):
      
      if isinstance(node, graph.NodeSet):
          ind = '  ' * indent
          out = [ind + 'cycle {'] + [
                  format_file_node(import_graph, n, indent + 1)
                  for n in node.nodes
          ] + [ind + '}']
          return '\n'.join(out)
      else:
          return format_file_node(import_graph, node, indent)
docs: Helper function for print_tree