input: Write a python function to find all indices of a given item in a list.
  assert find_all_indices([1, 2, 3, 4, 5, 2], 2) == [1, 5]
  assert find_all_indices([1, 1, 1, 1, 1], 1) == [0, 1, 2, 3, 4]
  assert find_all_indices([1, 2, 3, 4, 5], 6) == []
  assert find_all_indices([], 1) == []
output: def find_all_indices(lst, item):
      return [i for i, x in enumerate(lst) if x == item]