why the get_historical_klines() function feedback only the latest month of spot historical klines?

I tried to use the binance-python to get the historical klines of BTCUSDT by get_historical_klines() function on testnet, but the earliest data it feedback to me is a month ago. why is that?

Apologies but we don’t support 3rd party libraries, you might want to contact their community/support.
In case you want to use the official python connector, please refer to GitHub - binance/binance-connector-python: a simple connector to Binance Public API.