input: Write a function to find pairs of numbers in a list that add up to a target value.
  assert pairs_adding_to_target([1, 5, 9, 4], 10) == [[1, 9]]
  assert pairs_adding_to_target([2, 4, 3, 7, 5], 9) == [[2, 7], [4, 5]]
  assert pairs_adding_to_target([1, 2, 3, 4, 5], 6) == [[1, 5], [2, 4]]
output: def pairs_adding_to_target(nums, target):
      pairs = []
      seen = set()
      for num in nums:
          complement = target - num
          if complement in seen:
              pairs.append([complement, num])
          seen.add(num)
      return pairs