1 files changed, 4 insertions, 0 deletions
diff --git a/README.md b/README.md
index 7eebf3e..9cfc571 100644
--- a/README.md
+++ b/README.md
@@ -6,14 +6,18 @@ Define a dataclass:
 
 ```python
 from dataclasses import dataclass
+from typing import ClassVar
 
 @dataclass
 class User:
     name: str
     age: int
     active: bool
+    key: ClassVar[str] = "name"
 ```
 
+Note the `key` field which is used to denote that `name` should be used as the primary key field.
+
 Instantiate a new object:
 
 ```python