input: from typing import List, Any
  
  def first_non_repeating_char(lst: List[Any]) -> Any:
      """ Find the first non-repeating character in a given list.
      >>> first_non_repeating_char([1, 2, 3, 4, 4, 3, 2, 1])
      None
      """
output:     count_dict = {}
      for item in lst:
          if item in count_dict:
              count_dict[item] += 1
          else:
              count_dict[item] = 1
      
      for item in lst:
          if count_dict[item] == 1:
              return item
      
      return None