input: Write a function to find a pair of numbers from a given list that add up to a given target. If such a pair is found, return the pair as a list; otherwise, return None. The given list is sorted in ascending order.
  
  def find_pair(lst, target):
      for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return [lst[i], target-lst[i]]
      return None
  
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 8) == [2, 6]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 9) == [3, 6]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 10) == [4, 6]
  assert find_pair([1, 2, 3, 4, 4, 5, 6], 12) == None
  assert find_pair([], 5) == None
output: def find_pair(lst, target):
      for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return [lst[i], target-lst[i]]
      return None