Add typehint

freqtrade/persistence.py

@@ -377,7 +377,7 @@ class Trade(_DECL_BASE):
         )
 
     def update_fee(self, fee_cost: float, fee_currency: Optional[str], fee_rate: Optional[float],
-                   side) -> None:
+                   side: str) -> None:
         """
         Update Fee parameters. Only acts once per side
         """
@@ -394,7 +394,7 @@ class Trade(_DECL_BASE):
             if fee_rate is not None:
                 self.fee_close = fee_rate
 
-    def fee_updated(self, side) -> bool:
+    def fee_updated(self, side: str) -> bool:
         """
         Verify if this side (buy / sell) has already been updated
         """