Edits.

Author: WaVEV

django_mongodb/expressions.py

@@ -77,10 +77,11 @@ def query(self, compiler, connection):  # noqa: ARG001
 
 
 def ref(self, compiler, connection):  # noqa: ARG001
-    if isinstance(self.source, Col) and self.source.alias != compiler.collection_name:
-        prefix = f"{self.source.alias}."
-    else:
-        prefix = ""
+    prefix = (
+        f"{self.source.alias}."
+        if isinstance(self.source, Col) and self.source.alias != compiler.collection_name
+        else ""
+    )
     return f"${prefix}{self.refs}"