input: Write a python function to find the first non-repeating character in a list.
  assert first_non_repeating_char([1, 2, 3, 4, 4, 3, 2, 1]) == None
  assert first_non_repeating_char([1, 2, 3, 4, 5, 5, 4, 3, 2, 1, 6]) == 6
  assert first_non_repeating_char([4, 5, 4, 5, 7, 8, 8, 9]) == 7
output: def first_non_repeating_char(lst):
      count = {}
      for char in lst:
          count[char] = count.get(char, 0) + 1
      for char in lst:
          if count[char] == 1:
              return char
      return None