input: Write a function to check if any two numbers from a given list sum up to a target number. The function should return True if such a pair exists, otherwise return False.
  
  def check_sum(numbers, target):
      for i in range(len(numbers)):
          for j in range(i+1, len(numbers)):
              if numbers[i] + numbers[j] == target:
                  return True
      return False
  
  assert check_sum([1, 2, 3, 4], 5)==True
  assert check_sum([1, 2, 3, 4], 7)==True
  assert check_sum([1, 2, 3, 4], 8)==False
  assert check_sum([], 5)==False
  assert check_sum([10, 15, 3, 7], 17)==True
output: def check_sum(numbers, target):
      for i in range(len(numbers)):
          for j in range(i+1, len(numbers)):
              if numbers[i] + numbers[j] == target:
                  return True
      return False