input: Write a function to generate all possible combinations of a list of numbers taken k at a time.
  assert generate_combinations([1, 2, 3, 4], 3) == [(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)]
  assert generate_combinations([0, 1], 2) == [(0, 1)]
  assert generate_combinations([5, 6, 7, 8, 9], 4) == [(5, 6, 7, 8), (5, 6, 7, 9), (5, 6, 8, 9), (5, 7, 8, 9), (6, 7, 8, 9)]
output: def generate_combinations(numbers, k):
      from itertools import combinations
      return list(combinations(numbers, k))