input: Write a function to get all possible combinations of a list using itertools and return them as a list of tuples.
  assert get_combinations([1, 2, 3, 4], 2) == [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
  assert get_combinations([5, 6, 7], 2) == [(5, 6), (5, 7), (6, 7)]
  assert get_combinations(['a', 'b', 'c'], 2) == [('a', 'b'), ('a', 'c'), ('b', 'c')]
output: def get_combinations(lst, n):
      from itertools import combinations
      return list(combinations(lst, n))