input: 
  from typing import List, Tuple
  
  def find_pair(lst: List[int], target: int) -> Tuple[int, int]:
      """
      Find a pair of numbers from the given list that add up to the given target.
  
      :param lst: List of integers to search for the pair.
      :param target: The target sum for the pair.
      :return: A tuple containing the pair of numbers, or None if no such pair exists.
      
      >>> find_pair([1, 2, 3, 4, 4, 5, 6], 8)
      (4, 4)
      >>> find_pair([1, 2, 3, 4, 4, 5, 6], 20)
      None
      """
      for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return (lst[i], target - lst[i])
      return None
  
output:     for i in range(len(lst)):
          if (target - lst[i]) in lst[i+1:]:
              return (lst[i], target - lst[i])
      return None