input: Write a python function to generate all combinations of a given list and size using a utility function.
  assert combinations([1, 2, 3], 2) == [[1, 2], [1, 3], [2, 3]]
  assert combinations(["A", "B", "C"], 2) == [["A", "B"], ["A", "C"], ["B", "C"]]
  assert combinations([1, 2, 3, 4], 3) == [[1, 2, 3], [1, 2, 4], [1, 3, 4], [2, 3, 4]]
output: from itertools import combinations as itertools_combinations
  
  def combinations(lst, size):
      return [list(comb) for comb in itertools_combinations(lst, size)]