How to get apple music items size downloaded from apple music library without exporting the music items?

I am trying to retrieve the size of apple music items downloaded from the apple music library as iPod-library URL (ex. ipod-library://item/item.m4a?id=8536687568586472929) but without exporting to the document directory, I am unable to get the size. I tried the below code.

Code: 

do { 
    let resources = try url.resourceValues(forKeys:[.fileSizeKey]) 
    let fileSize = resources.fileSize ?? 0 print ("size \(fileSize)") 
    } catch {
    print("Error: \(error)") 
    } 
}

Output: Couldn't fetch size for file The file “item.m4a” couldn’t be opened because there is no such file. Size: 0