feat: adds support to automatically fallback to the default encoding (#596)

* feat: adds support to automatically fallbackk to the default encoding

* fix: use the correct method

src/crewai/utilities/token_counter_callback.py

@@ -42,9 +42,9 @@ class TokenCalcHandler(BaseCallbackHandler):
     def on_llm_start(
         self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
     ) -> None:
-        if "gpt" in self.model:
+        try:
             encoding = tiktoken.encoding_for_model(self.model)
-        else:
+        except KeyError:
             encoding = tiktoken.get_encoding("cl100k_base")
 
         if self.token_cost_process is None: