Remove lines from a list that doesn't appear in another list

[tim.stark]

Without your definition, it’s hard to tell you what went wrong…

Have a look at this: Same problem, keeping lines which appear in both lists.

Developing the 3d isovist to optimization

Im trying to make a version of isovist that can give me the optimize place for my building to be maximum seen from a path. I need a componant that could give me a list with the items that are included in two other lists. I am not sure if this is the only proplem, if you have any other idea 2D 3D isovist-1.gh (38.0 KB) isovist-1.3dm (66.1 KB)