input: Write a Python function that duplicates a list contained in a single-element tuple.
  assert lcopy([1, 2, 3]) == [1, 2, 3]
  assert lcopy([4, 8, 2, 10, 15, 18]) == [4, 8, 2, 10, 15, 18]
  assert lcopy([4, 5, 6]) == [4, 5, 6]
output: def lcopy(lst):
      return lst[:]