Merge pull request #5809 from kenjis/fix-docs-entity

docs: add note about `attributes` in Entity

Author: kenjis

user_guide_src/source/models/entities.rst

@@ -31,6 +31,8 @@ Assume you have a database table named ``users`` that has the following schema::
     password    - string
     created_at  - datetime
 
+.. important:: ``attributes`` is a reserved word for internal use. If you use it as a column name, the Entity does not work correctly.
+
 Create the Entity Class
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