chore: fix pylint error in CI

Author: SunsetWolf

qlib/contrib/strategy/signal_strategy.py

@@ -619,12 +619,10 @@ def get_last_n(li, n):
             def filter_stock(li):
                 return li
 
-        import copy as _copy  # local alias for deepcopy
-
         # Use instance configuration; keep behavior unchanged (no external kwargs expected here)
-        risk_aversion = _copy.deepcopy(getattr(self, "risk_aversion", None))
+        risk_aversion = copy.deepcopy(getattr(self, "risk_aversion", None))
 
-        current_temp: Position = _copy.deepcopy(self.trade_position)
+        current_temp: Position = copy.deepcopy(self.trade_position)
 
         # Build current long/short lists by sign of amount
         current_stock_list = current_temp.get_stock_list()