GetFile does not work on FileSystemApi

I'm studying FILEAPI at Monaca, but I can't create files even if I look at the documents on the website.
https://docs.monaca.io/ja/reference/cordova_6.2/file/

I tried to create a txt file using this document, but getFile didn't work.
The operating system is iOS and I use Library for storage.
You can get a list of files.
Also, I probably created a folder called File in the Library directory when I used getFile.I don't know why this happens.
This may be a rudimentary question, but I appreciate your cooperation.