object '.session' is not found in groupframe

[detsutut]

When I follow the code with my own csv.file (which I implemented by adapting the getFrames() to use file.choose instead of choose.files), when I run the line
framelines = lapply(movies,function(movie){groupframes(movie,seconds = 0.05)})
I get an error saying that in the groupframe function: function(frames,seconds=NULL,fps=.session$fps) -> object '.session' is not found.

Originally posted by @Mette-Jill in #2 (comment)