input: Write a function to find two numbers in a list that add up to a target sum.
  assert two_sum([1, 3, 5, 7, 9], 12) == (5, 7)
  assert two_sum([2, 4, 6, 8], 10) == (2, 8)
  assert two_sum([0, -1, 2, -3, 1], -2) == (-1, -1)
output: def two_sum(nums, target):
      num_map = {}
      for num in nums:
          complement = target - num
          if complement in num_map:
              return (complement, num)
          num_map[num] = True