input: Write a function to check if any two numbers from a given list sum up to a given target number. The function should return True if such two numbers exist, 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], 9) == True
  assert check_sum([1, 2, 3, 4, 5], 10) == False
  assert check_sum([1, 2, 3, 4, 5], 7) == True
  assert check_sum([], 5) == False
  assert check_sum([5], 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