Two thoughts:

1.) I doubt that getInnerPolygons is tail recursive, because the recursive call to getInnerPolygons within flatMap is not the last statement to be executed. This is flatMap itself (but I may be wrong). Recursive calls to functions which are not tail recursive can lead to a stack overflow, when recursion is going deeper. In this case recursion can't be eliminated by the compiler.

2.) You could write

(0 to geometry.GetGeometryCount())

instead of

Iterator.range(0, geometry.GetGeometryCount())

to create a range. This is slightly shorter.

Two thoughts:

1. I doubt that getInnerPolygons is tail recursive, because the recursive call to getInnerPolygons within flatMap is not the last statement to be executed. This is flatMap itself (but I may be wrong). Recursive calls to functions which are not tail recursive can lead to a stack overflow, when recursion is going deeper. In this case recursion can't be eliminated by the compiler.

2. You could write

   (0 to geometry.GetGeometryCount())
   

instead of

    Iterator.range(0, geometry.GetGeometryCount())

to create a range. This is slightly shorter.