No. Python scripts cannot be backtested using the MT5 platform. Only EAs written in MQL can be backtested using MT5.
if script working is Python then, it can not backtested
if EA trade main is MQL5 and call to calculate at python, then is can possible to backtesting
The point of a python API is to use python tools, not MT5. If you want to use only MT5 then you need to write your algos in MQL. You use python because
you want to backtest and trade using python libraries.