I have a question about the meaning of the symbol (i).

It's called bar It is usually used as a delimiter. This is because it is a special text that can be typed directly from the keyboard without much effort, and it seems that there will be no problem if it is used as a delimiter.

What colon and bar have in common is that they are often used as separators. However, since there is a lot of room for detection in the actual user input, it is ambiguous to write it as a delimiter unless there is a reason, but in the case of bars, users rarely use that strange symbol, right? So it's convenient because there's no problem if you connect the user's inputs directly to | or split them.