fixing unnecessary import of ProductTree

[x-64]

Line from sage.rings.generic import ProductTree in montgomery_isogenies/kummer_isogeny.py fails but is not necessary.
Fixes #144

[Copilot]

Pull request overview

This PR attempts to fix a failing import by commenting out the ProductTree import from sage.rings.generic. However, ProductTree is actually used in the code on line 428 within the KummerLineIsogeny_VeluSqrt._hI_precomputation method. While the challenge code doesn't trigger this code path due to using small primes (< 587) with a default threshold of 1500, commenting out the import will break the VéluSqrt functionality and cause a NameError if that code path is ever executed.

Key Changes

• Commented out the import statement for ProductTree from sage.rings.generic

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Commenting out the ProductTree import will cause a NameError when KummerLineIsogeny_VeluSqrt is used (line 428). While the challenge code uses only small primes (< 587) and the default threshold is 1500, making VeluSqrt unused in normal operation, commenting out this import breaks the VeluSqrt functionality entirely. Consider either: 1) importing ProductTree from the correct location if the path has changed in newer Sage versions, 2) implementing a local ProductTree class, or 3) removing the VeluSqrt class entirely if it's not needed.

Suggested change

	#from sage.rings.generic import ProductTree
	from sage.rings.generic import ProductTree

[x-64]

This code branch is never used and by commenting out the import, the solution becomes possible. The platform has Sage 10.6 but this struggles with SUID. Using the Python 3.8, only Sage 9.0 from 2020 is available. As ProductTree became available around Sage 9.7 in 2022, this seems the easiest way to proceed. Removing the entire class seems much to desructive.