input: Write a python function to calculate the average of a list excluding None values.
  assert avg([30, 28, 40, 10, 0, None, 33, None]) == 23.5
  assert avg([None, None, None]) == 0  # or adjust according to your error handling
  assert avg([10, 20, 30, 40, 50]) == 30.0
output: def avg(lst):
      filtered_lst = [x for x in lst if x is not None]
      if not filtered_lst:
          return 0
      return sum(filtered_lst) / len(filtered_lst)