input: Write a function to check if any two numbers from the provided list sum up to the target. If such a pair exists, return True; otherwise, return False.
  assert check_sum([1, 2, 3, 4], 5)==True
  assert check_sum([4, 7, 8, 1], 15)==False
  assert check_sum([10, 20, 30, 40], 60)==True
  assert check_sum([1, 2, 3, 4], 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