Returns a string list of metadata values contained in an audio file.
		
		app.GetMetadata(
			
file,
			
keys )
			→ 
string: comma “,” separated
		See Also: CreateMediaPlayer
	 
	string: path to file or folder ( “/absolute/...” or “relative/...” )
	string: comma “,” separated: “album”, “artist”, “genre”, “title”, “composer”, “author”, “duration”, “bitrate”, “width”, “height”