Fix using in operator with find method

src/api/categories.py

@@ -2,6 +2,7 @@ from datetime import datetime
 from typing import Annotated, final
 
 from beanie import PydanticObjectId
+from beanie.odm.operators.find.comparison import In
 from fastapi import APIRouter, Body, HTTPException, Response, status
 from pydantic import BaseModel, StringConstraints, field_validator
 from pydantic_extra_types.color import Color
@@ -158,7 +159,7 @@ async def delete_category(category_id: PydanticObjectId, user: CurrentUserDep) -
     # First remove the association to this category by events
     # (this may leave the event without a category, however that's fine, as event category is optional
     # and it's far more sensible solution than deleting all events with this category)
-    events = await Event.find(category in Event.categories).to_list()
+    events = await Event.find(In(category, Event.categories)).to_list()
     for event in events:
         new_categories = list(event.categories)
         new_categories.remove(category)