Build fails when compiled under Java 13. Compiler errors indicate the problem is caused by using underscores in assignments: as of release 9, '_' is a keyword, and may not be used as an identifier
I believe the if statement should be if child.region.overlaps instead of if child.region.overlaps in quad.py. if child.region.overlaps returns a boolean and does the comparison to check for overlaping regions. child.region.overlaps returns a region.