input: def find_pair(numbers: List[int], target: int) -> List[int]:
      """Given a list of numbers and a target number, find and return a pair of numbers 
      from the list that add up to the target number.
      >>> find_pair([1, 2, 3, 4, 4, 5, 6], 8)
      [4, 4]
      """
output:     seen = {}
      for num in numbers:
          complement = target - num
          if complement in seen:
              return [complement, num]
          seen[num] = True
      return []