input: Write a function to check if any two numbers from a given list sum up to a target number. If such a pair exists, return True; otherwise, return False. If the list is empty, 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], 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], 10) == True
  assert check_sum([], 5) == False
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