input: Write a function to find a pair of numbers from a given list that add up to a specified target number. If such a pair exists, return the pair as a list, otherwise return an empty list. If the list is empty or contains less than two elements, return an empty list.
  def find_pair(lst, target):
      if len(lst) < 2:
          return []
      for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return [lst[i], target-lst[i]]
      return []
  
  assert find_pair([1,2,3,4,4,5,6], 8) == [2, 6]
  assert find_pair([1,2,3,4,4,5,6], 7) == [1, 6]
  assert find_pair([1,2,3,4,4,5,6], 10) == []
  assert find_pair([], 8) == []
  assert find_pair([1], 1) == []
output: def find_pair(lst, target):
      if len(lst) < 2:
          return []
      for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return [lst[i], target-lst[i]]
      return []