upd

chess0.py

@@ -133,8 +133,8 @@ class ChessManager:
  
         move = None
 
-        if self.board.attackers_mask(chess.WHITE, self.board.king(chess.BLACK)) != 0:
-            move = self.board.king(chess.BLACK)
+        if session.board.attackers_mask(chess.WHITE, session.board.king(chess.BLACK)) != 0:
+            move = session.board.king(chess.BLACK)
           
         if session.board.is_check():
             return chess.svg.board(session.board, size=size, lastmove=move, arrows=arrows, fill={checker: "#cc0000cc" for checker in session.board.checkers()}, check=session.board.king(session.board.turn))