input: Write a function to find pairs in a list of numbers that add up to a given threshold.
  assert find_pairs_threshold([2, 3, 5, 7, 8], 10) == [(2, 8), (3, 7)]
  assert find_pairs_threshold([1, 2, 3, 4, 5], 6) == [(1, 5), (2, 4)]
  assert find_pairs_threshold([0, -1, 2, -3, 1], -1) == [(0, -1), (2, -3)]
  assert find_pairs_threshold([10, 20, 10, 40, 50, 60, 70], 50) == [(10, 40)]
output: def find_pairs_threshold(numbers, threshold):
      pairs = []
      seen = set()
      for number in numbers:
          complement = threshold - number
          if complement in seen:
              pairs.append((complement, number))
          seen.add(number)
      return pairs