input: Write a python function to check if there is a pair of numbers in a list that add up to a given sum.
  assert check_pair([2, 4, 6, 5], 8) == True
  assert check_pair([1, 2, 3, 9], 8) == False
  assert check_pair([1, 2, 4, 4], 8) == True
  assert check_pair([1, 2, 3, 4, 5], 10) == False
output: def check_pair(numbers, target_sum):
      seen = set()
      for num in numbers:
          if target_sum - num in seen:
              return True
          seen.add(num)
      return False