upd

markov.py

@@ -28,9 +28,9 @@ class Markov:
         return self.chain is not None
 
     def generate(self, init_state=None):
-        if isinstance(init_state, str):
-            init_state = self.tokenize(init_state)
-
+        if init_state is not None:
+            init_state = tuple(self.tokenize(init_state))
+        
         words = self.chain.walk(init_state)
         if not words:
             return self.generate()