diff --git a/docs/examples/schema_with_field.py b/docs/examples/schema_with_field.py
index 9288efd8cd..860903e55b 100644
--- a/docs/examples/schema_with_field.py
+++ b/docs/examples/schema_with_field.py
@@ -1,5 +1,5 @@
 # output-json
-from typing import Optional
+from typing import Any, Callable, Dict, Generator, Optional
 
 from pydantic import BaseModel, Field
 from pydantic.fields import ModelField
@@ -7,18 +7,20 @@
 
 class RestrictedAlphabetStr(str):
     @classmethod
-    def __get_validators__(cls):
+    def __get_validators__(cls) -> Generator[Callable, None, None]:
         yield cls.validate
 
     @classmethod
-    def validate(cls, value, field: ModelField):
+    def validate(cls, value: str, field: ModelField):
         alphabet = field.field_info.extra['alphabet']
         if any(c not in alphabet for c in value):
             raise ValueError(f'{value!r} is not restricted to {alphabet!r}')
         return cls(value)
 
     @classmethod
-    def __modify_schema__(cls, field_schema, field: Optional[ModelField]):
+    def __modify_schema__(
+        cls, field_schema: Dict[str, Any], field: Optional[ModelField]
+    ):
         if field:
             alphabet = field.field_info.extra['alphabet']
             field_schema['examples'] = [c * 3 for c in alphabet]