I tried with the following function that produce the power set, the set of all possible subset, in the similar spirit of the function that create all the possible permutations:

Explain simply what this function does:

  ```
  def func(ls):
    if len(ls) == 0:
      return [ [] ]
    elif len(ls) == 1:
      return [ [], ls ]
    else:
      x = ls[-1]
      prem = func(ls[:-1])
      p = prem[:]
      for e in prem:
        p.append(e + [x])
      return p
  ```

GPT-4 aced the answer which is remarkable but I think that it is because it have seen this "pattern" in its learning database being a fundamental function in mathematics.

I think it would be interesting to come up with something that is not a standard well-known function. I have to think to something else.