diff --git a/src/models/category.py b/src/models/category.py
index f11b709..4c64c1b 100644
--- a/src/models/category.py
+++ b/src/models/category.py
@@ -257,6 +257,7 @@ class CategoryTree(BaseModel):
         return result
 
 def build_category_tree(transactions: list[Transaction]) -> list[CategoryTree]:
+    # TODO: loop through flat list a build a category tree
     result = []
     for transaction in transactions:
         pass