Similar Topic:
from what I understand that with a selection and a specified document interface:
var Counter = PolylineFromSelection.autoJoinSegments(di, 0.001);
simply would create the polys from the selection in the di and returns how much that are created.
So, probably the op is part of the method. 
Andrew’s note:
Please keep in mind that PolylineFromSelection is not part of the public API but part of the proprietary API of QCAD Professional.
Feel free to call this from your script, but keep in mind that this API might change in a future version.
Regards,
CVH