Google Drive - Backing up to existing folder not in root results in duplicate directory being created
Summary
When entering a folder in the preferences dialog, if an existing path is entered, Deja Dup will always create a new folder structure, even if the existing path exists (allowed because Google Drive files and folders are unique by ID not name).
Reproduction Steps
This can be reproduced by creating a folder in Google Drive (e.g. backups) and then a folder inside that folder (e.g. laptop), entering the path in the preferences dialog (e.g. backups/laptop) and attempting a backup.
Debug Information
I'm not familiar with this project (or Vala) so I couldn't easily verify scanning through the source files, but it seems as implemented PyDrive2's ListFile only searches the root folder ('root' in parents query term) for a folder with name equal to the path entered. I think a solution might be to implement logic to split the path by delimiter, setting the name query term to only the last element and adding all the elements to the parents query term and passing to ListFile.
(See https://developers.google.com/drive/api/guides/ref-search-terms#file_properties for Query Term documentation)