code: def get_iter_string_reader(stdin):
      
      bufsize = 1024
      iter_str = (stdin[i:i + bufsize] for i in range(0, len(stdin), bufsize))
      return get_iter_chunk_reader(iter_str)
docs: return an iterator that returns a chunk of a string every time it is
      called.  notice that even though bufsize_type might be line buffered, we're
      not doing any line buffering here.  that's because our StreamBufferer
      handles all buffering.  we just need to return a reasonable-sized chunk.