input: Write a function to check if any two numbers from a given list sum up to a target number. If they do, return True, otherwise return False. The function should take two parameters, the list of numbers and the target number.
  
  assert check_sum([3, 4, 5, 1, 2], 9)==True
  assert check_sum([3, 5, 10, 1, 2], 7)==True
  assert check_sum([4, 3, 1, 2], 8)==False
  assert check_sum([3, 5, 4, 1, 2], 10)==False
  assert check_sum([], 5)==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