input: Write a function to find a pair of numbers from the given list that add up to the given target. If such a pair exists, return them as a list. If no such pair exists, return an empty list. The function should be named `find_pair` and take two arguments: the list of numbers (`lst`) and the target number (`target`).
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 8) == [4, 4]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 10) == [4, 6]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 7) == [4, 3]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 15) == []
  assert find_pair([], 8) == []
output: def find_pair(lst, target):
      seen = set()
      for num in lst:
          complement = target - num
          if complement in seen:
              return [complement, num]
          seen.add(num)
      return []