code: def ReadTag(buf, pos):
    
    try:
      start = pos
      while ORD_MAP_AND_0X80[buf[pos]]:
        pos += 1
      pos += 1
      return (buf[start:pos], pos)
    except IndexError:
      raise ValueError("Invalid tag")
docs: Read a tag from the buffer, and return a (tag_bytes, new_pos) tuple.