input: Write a function to find the first non-repeating character in a given list. If there is no non-repeating character return None.
  assert first_non_repeating_char([1, 2, 3, 4, 4, 3, 2, 1])==None
  assert first_non_repeating_char([1, 2, 3, 4, 5, 3, 4, 1, 2])==5
  assert first_non_repeating_char([9, 2, 8, 2, 9, 3, 8])==3
  assert first_non_repeating_char([1, 1, 2, 2, 3, 3, 4])==4
  assert first_non_repeating_char([])==None
output: def first_non_repeating_char(lst):
      count = {}
      for item in lst:
          if item in count:
              count[item] += 1
          else:
              count[item] = 1
      for item in lst:
          if count[item] == 1:
              return item
      return None