Simplify liquidation price calculation

freqtrade/exchange/exchange.py

@@ -2055,23 +2055,23 @@ class Exchange:
         except ccxt.BaseError as e:
             raise OperationalException(e) from e
 
-    def leverage_prep(
+    def get_interest_rate(self) -> float:
+        """
+        Calculate interest rate - necessary for Margin trading.
+        """
+        return 0.0
+
+    def get_liquidation_price(
             self,
             pair: str,
             open_rate: float,
             amount: float,  # quote currency, includes leverage
             leverage: float,
             is_short: bool
-    ) -> Tuple[float, Optional[float]]:
+    ) -> Optional[float]:
 
-        # if TradingMode == TradingMode.MARGIN:
-        #     interest_rate = self.get_interest_rate(
-        #         pair=pair,
-        #         open_rate=open_rate,
-        #         is_short=is_short
-        #     )
-        if self.trading_mode == TradingMode.SPOT:
-            return (0.0, None)
+        if self.trading_mode in (TradingMode.SPOT, TradingMode.MARGIN):
+            return None
         elif (
             self.margin_mode == MarginMode.ISOLATED and
             self.trading_mode == TradingMode.FUTURES
@@ -2086,7 +2086,7 @@ class Exchange:
                 mm_ex_1=0.0,
                 upnl_ex_1=0.0,
             )
-            return (0.0, isolated_liq)
+            return isolated_liq
         else:
             raise OperationalException(
                 "Freqtrade only supports isolated futures for leverage trading")
@@ -2231,7 +2231,7 @@ class Exchange:
             return 0.0
 
     @retrier
-    def get_liquidation_price(
+    def get_or_calculate_liquidation_price(
         self,
         pair: str,
         # Dry-run