The same way as with Pydantic models, you declare class attributes with type annotations, and possibly default values.

You can use all the same validation features and tools you use for Pydantic models, like different data types and additional validations with `Field()`.

=== "Pydantic v2"

    ```Python hl_lines="2  5-8  11"
    {!> ../../../docs_src/settings/tutorial001.py!}
    ```

=== "Pydantic v1"

```Python
item: Item
```

...and with that single declaration you get:

* Editor support, including:
    * Completion.
    * Type checks.
* Validation of data:
    * Automatic and clear errors when the data is invalid.
    * Validation even for deeply nested JSON objects.

  // Name must be a qualified name consisting of alphanumeric characters, '-', '_' or '.', and
  // must start and end with an alphanumeric character (e.g. 'MyName',  or 'my.name',  or
  // '123-abc', regex used for validation is '([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]') with an
  // optional DNS subdomain prefix and '/' (e.g. 'example.com/MyName')
  //
  // Required.
  optional string name = 1;

    override fun getName(): String =
        delegate.name

    override fun file(path: Any): File =
        delegate.file(path)

    override fun file(path: Any, validation: PathValidation): File =
        delegate.file(path, validation)

    override fun findProject(path: String): Project? =
        delegate.findProject(path)

    override fun getPlugins(): PluginContainer =
        delegate.plugins

Поля `example` как такового не существует в стандартах **JSON Schema**. В последних версиях JSON-схемы определено поле <a href="https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.9.5" class="external-link" target="_blank">`examples`</a>, но OpenAPI 3.0.3 основан на более старой версии JSON-схемы, которая не имела поля `examples`.

  // Name must be a qualified name consisting of alphanumeric characters, '-', '_' or '.', and
  // must start and end with an alphanumeric character (e.g. 'MyName',  or 'my.name',  or
  // '123-abc', regex used for validation is '([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]') with an
  // optional DNS subdomain prefix and '/' (e.g. 'example.com/MyName')
  //
  // Required.
  optional string name = 1;

    return
  }
}

// -----

// Tests malformed initializer function that has a fetch other than
// tf_executor::ControlType.

// expected-error @+1 {{Validation on initializer functions failed.}}
module attributes {tf.versions = {bad_consumers = [], min_consumer = 12 : i32, producer = 1228 : i32}, tf_saved_model.semantics} {

        internalReporter.create {
            id(
                "configuration-cache-" + DeprecationMessageBuilder.createDefaultDeprecationId(message),
                message,
                GradleCoreProblemGroup.validation()
            )
            contextualLabel(message)
            documentOfProblem(problem)
            locationOfProblem(problem)
            severity(severity.toProblemSeverity())

            ],
            "msg": "value is not a valid integer",
            "type": "type_error.integer"
        }
    ]
}
```

вы получите текстовую версию:

```
1 validation error
path -> item_id
  value is not a valid integer (type=type_error.integer)
```

#### `RequestValidationError` или `ValidationError`

!!! warning "Внимание"

# disable_pgv: disables protoc-gen-validation. This is not used buts adds many MB to Envoy protos
# not set vtprotobuf: this adds some performance improvement, but at a binary cost increase that is not worth it for the agent
AGENT_TAGS=agent,disable_pgv
# disable_pgv: disables protoc-gen-validation. This is not used buts adds many MB to Envoy protos