input: Write a function to filter a list by removing elements that have more than 3 characters or contain the letter 'k'.
  assert filter_list(['cat', 'dog', 'elephant', 'kettle', 'frog']) == ['cat', 'dog']
  assert filter_list(['kite', 'bat', 'rat', 'duck']) == ['bat', 'rat']
  assert filter_list(['sky', 'key', 'lock', 'box']) == ['sky', 'box']
output: def filter_list(lst):
      return [item for item in lst if len(item) <= 3 and 'k' not in item]