input: Write a function to find a pair of numbers from the given list that add up to the given target. If a pair is found, return the pair as a list; otherwise, return None.
  
  def find_pair(lst, target):
      for num in lst:
          if (target - num) in lst and (target - num) != num:
              return [num, target - num]
      return None
  
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 8) == [2, 6]
  assert find_pair([3, 5, 2, 4], 6) == [2, 4]
  assert find_pair([1, 5, 7, 9], 14) == [5, 9]
  assert find_pair([2, 2, 3, 1, 4], 7) == [3, 4]
  assert find_pair([1], 5) == None
  assert find_pair([], 7) == None
output: def find_pair(lst, target):
      for num in lst:
          if (target - num) in lst and (target - num) != num:
              return [num, target - num]
      return None