PYTHON-4834 Add __repr__ to IndexModel

- Prefer arg over kwarg for keys

Author: aclark4life

pymongo/operations.py

@@ -775,8 +775,8 @@ def document(self) -> dict[str, Any]:
 
     def __repr__(self) -> str:
         return "%s(%s%s)" % (
-            self.__class__.__name__,                                               
-            "keys=%s" % self.document["key"],
+            self.__class__.__name__,
+            self.document["key"],
             "".join(
                 [
                     ", %s=%r" % (key, value)