Mod(3 i, 2) unchanged Mod(3 i, 2) should reduce to Mod(i, 2) (as reported in this…

Mod(3 i, 2) unchanged Mod(3 i, 2) should reduce to Mod(i, 2) (as reported in this…: a task in Lego-RL-SWE-Bench-Verified (Harbor dataset). Returns correct result to Mod(3 i, 2). modified the mod.py to return correct answer to Mod(3 i, 2). added a test (All as suggested by @smichr )