refactor stepfun cv model (#1751)

### What problem does this PR solve?

refactor stepfun cv model

### Type of change

- [x] Refactoring

Co-authored-by: Zhedong Cen <cenzhedong2@126.com>

rag/llm/cv_model.py

@@ -622,27 +622,13 @@ class NvidiaCV(Base):
             }
         ]
 
-class StepFunCV(Base):
+class StepFunCV(GptV4):
     def __init__(self, key, model_name="step-1v-8k", lang="Chinese", base_url="https://api.stepfun.com/v1"):
         if not base_url: base_url="https://api.stepfun.com/v1"
         self.client = OpenAI(api_key=key, base_url=base_url)
         self.model_name = model_name
         self.lang = lang
 
-    def describe(self, image, max_tokens=4096):
-        b64 = self.image2base64(image)
-        prompt = self.prompt(b64)
-        for i in range(len(prompt)):
-            for c in prompt[i]["content"]:
-                if "text" in c: c["type"] = "text"
-
-        res = self.client.chat.completions.create(
-            model=self.model_name,
-            messages=prompt,
-            max_tokens=max_tokens,
-        )
-        return res.choices[0].message.content.strip(), res.usage.total_tokens
-
 class LmStudioCV(GptV4):
     def __init__(self, key, model_name, base_url, lang="Chinese"):
         if not base_url: