Add sign_magneticfield validation to exchange_legendre.py#4

skilledwolf merged 2 commits intoFixes_B_fieldskilledwolf/quantumhall_matrixelements:Fixes_B_fieldfrom

copilot/sub-pr-2-againskilledwolf/quantumhall_matrixelements:copilot/sub-pr-2-againCopy head branch name to clipboard