How would you find permutations of all possible 1) lengths, 2) orders, and 3) from multiple lists?

permutations.py

import itertools

# Permutations of multiple lists
# https://stackoverflow.com/q/2853212
s=[ [ 'a', 'b', 'c'], ['d'], ['e', 'f'] ]
for l in list(itertools.product(*s)):
    print(l)


# Permutations of all possible sizes of a list
# https://stackoverflow.com/a/5898031/99923
s = [1, 2, 3]
for L in range(0, len(s)+1):
    for subset in itertools.permutations(s, L):
        print(subset)


# Permutations of all possible lenghts and orders of a multiple lists
# https://stackoverflow.com/q/50242147/99923
s=[ [ 'a', 'b', 'c'], ['d'], ['e', 'f'] ]
s = [x for y in s for x in y]

for L in range(0, len(s)+1):
    for subset in itertools.permutations(s, L):
        print(subset)