https://stackoverflow.com/questions/5369723/multi-level-defaultdict-with-variable-depth
` from collections import defaultdict
nested_dict = lambda: defaultdict(nested_dict) nest = nested_dict()
nest[0][1][2][3][4][5] = 6 `
https://stackoverflow.com/questions/5369723/multi-level-defaultdict-with-variable-depth
` from collections import defaultdict
nested_dict = lambda: defaultdict(nested_dict) nest = nested_dict()
nest[0][1][2][3][4][5] = 6 `