Face-SketchArc_1_2f... what mean 2f?

Dear all,

I'm going through the python code generated by shaper in order to understand its structure.

I arrived on this command:

Face_1_objects = [model.selection("FACE", "Sketch_1/Face-SketchArc_1_2f-SketchLine_2f-SketchLine_3f-SketchLine_1r"),
                  model.selection("FACE", "Sketch_1/Face-SketchLine_5f-SketchArc_2_2r-SketchLine_5f-SketchLine_6f-SketchLine_7f-SketchLine_4f-SketchLine_2r-SketchArc_1_2r"),
                  model.selection("FACE", "Sketch_1/Face-SketchLine_5f-SketchArc_2_2f")]

Of course, my code contains objects such as SketchArc_1 or SketchLine_5 being part of Sketch_1. My only concern is the meaning of the letter "f" or "r" following a line object, as well as the "_2f" or "_2r".

What does that mean, when setting up this string defining the face? f for forward and r for reversed corresponding to the direction of the added entity in the added entity forming the surrounding of the face?

Also, and maybe the most important one... where can I find this information by myself?

I thank you a lot for your support.

Regards