How to save game in unity using google play services plugin?

Question

Unity

I want to make cloud saves for a mobile game. In the description for the plugin on the github there is a function, as I understand it, we save it with the help of it:

SaveGame(ISavedGameMetadata game, byte[] savedData, System.TimeSpan totalPlaytime)

savedData - the save data itself,
totalPlaytime - it's not clear why, but time is the total time spent in the game by the player (for all time)?
ISavedGameMetadata game - what is this (how to get, create)?
Maybe there are examples of how to use it?