bisect_plane question

I am using bmesh.ops.bisect_plane to cut an object with a plane.

Is there any way to retrieve the vertices in the cut plane of the cut object? (I want to use them to close the cut with a face).

I cant see them in the returned data (ret = bmesh.ops.bisect_plane).
And if I look at the cut object in edit mode, they are not selected either.

Many thanks for any help

if you are cutting a manifold mesh, you could select all non-manifold edges. Just a quick thought.