Added missing import

api.py

@@ -3,7 +3,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import StreamingResponse
 from fastapi.encoders import jsonable_encoder
 from pydantic import BaseModel, Field, EmailStr, validator, field_validator
-from typing import List, Optional, Dict
+from typing import List, Optional, Dict, ClassVar
 from datetime import date, datetime
 from enum import Enum, IntEnum
 import uvicorn