input: Write a function to check if any two numbers from the list sum up to the target. If there are two numbers that sum to the target, return True, otherwise return False.
  assert check_sum([1, 2, 3, 4], 7) == True
  assert check_sum([1, 2, 3, 4], 8) == False
  assert check_sum([5, 10, 15, 20], 25) == True
  assert check_sum([1, 3, 5, 7], 4) == True
  assert check_sum([2, 4, 6, 8], 9) == False
output: def check_sum(nums, target):
      seen = set()
      for num in nums:
          if target - num in seen:
              return True
          seen.add(num)
      return False