fixbug: METAGPT model is None

fixbug: add METAGPT model calc usage logic

metagpt/provider/metagpt_api.py

@@ -5,12 +5,30 @@
 @File    : metagpt_api.py
 @Desc    : MetaGPT LLM provider.
 """
-from metagpt.config import LLMProviderEnum
+from openai.types import CompletionUsage
+
+from metagpt.config import CONFIG, LLMProviderEnum
 from metagpt.provider import OpenAILLM
 from metagpt.provider.llm_provider_registry import register_provider
+from metagpt.utils.exceptions import handle_exception
 
 
 @register_provider(LLMProviderEnum.METAGPT)
 class MetaGPTLLM(OpenAILLM):
     def __init__(self):
         super().__init__()
+        self.model = CONFIG.DEPLOYMENT_NAME
+
+    def _calc_usage(self, messages: list[dict], rsp: str) -> CompletionUsage:
+        usage = CompletionUsage(prompt_tokens=0, completion_tokens=0, total_tokens=0)
+        if not CONFIG.calc_usage:
+            return usage
+
+        # The current billing is based on usage frequency. If there is a future billing logic based on the
+        # number of tokens, please refine the logic here accordingly.
+
+        return usage
+
+    @handle_exception
+    def _update_costs(self, usage: CompletionUsage):
+        pass