update example output

README.md

@@ -182,25 +182,38 @@ components:
 
 `model.py`:
 ```python
+# generated by datamodel-codegen:
+#   filename:  api.yaml
+#   timestamp: 2019-07-23T14:23:18+00:00
+
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+
 class Pet(BaseModel):
     id: int
     name: str
-    tag: str = None
+    tag: Optional[str] = None
+
 
+class Pets(BaseModel):
+    __root__: List[Pet]
 
-Pets = List[Pet]
 
 class Error(BaseModel):
     code: int
     message: str
 
 
 class api(BaseModel):
-    apiKey: str = None
-    apiVersionNumber: str = None
+    apiKey: Optional[str] = None
+    apiVersionNumber: Optional[str] = None
 
 
-apis = List[api]
+class apis(BaseModel):
+    __root__: List[api]
 ```
 
 ## Development