update base model for atomic

Author: mahenzon

fastapi_jsonapi/atomic/schemas.py

@@ -1,10 +1,8 @@
 from typing import List, Literal, Optional, Union
 
-from pydantic import Field, root_validator
+from pydantic import BaseModel, Field, root_validator
 from starlette.datastructures import URLPath
 
-from fastapi_jsonapi.schema_base import BaseModel
-
 
 class OperationRelationshipSchema(BaseModel):
     id: str = Field(default=..., description="Related object ID")