code: def mark_list(line: str) -> List[int]:
      
      marks = []
      for idx, car in enumerate(list(line)):
          if car != " ":
              marks.append(idx)
      return marks
docs: Given a string, return a list of index positions where a character/non blank space exists.
  
      :param line:
      :return:
  
      >>> mark_list(" a b c")
      [1, 3, 5]