input: Write a python function to generate all subsets of a set.
  assert generate_subset([1, 2, 3])==[[], [1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3]]
  assert generate_subset([4, 5])==[[], [4], [5], [4, 5]]
  assert generate_subset([])==[[]]
  assert generate_subset([1])==[[], [1]]
output: def generate_subset(s):
      res = [[]]
      for num in s:
          res += [curr + [num] for curr in res]
      return res