def on_enter(
        self,
        input: Any,
        *,
        strict: bool | None = None,
        from_attributes: bool | None = None,
        context: dict[str, Any] | None = None,
        self_instance: Any | None = None,
        by_alias: bool | None = None,
        by_name: bool | None = None,
    ) -> None:
        """Callback to be notified of validation start, and create an instance of the event handler.

        Args:
            input: The input to be validated.
            strict: Whether to validate the object in strict mode.
            from_attributes: Whether to validate objects as inputs by extracting attributes.
            context: The context to use for validation, this is passed to functional validators.
            self_instance: An instance of a model to set attributes on from validation, this is used when running
                validation from the `__init__` method of a model.
            by_alias: Whether to use the field's alias to match the input data to an attribute.
            by_name: Whether to use the field's name to match the input data to an attribute.
        """
        pass
Callback to be notified of validation start, and create an instance of the event handler.

        Args:
            input: The input to be validated.
            strict: Whether to validate the object in strict mode.
            from_attributes: Whether to validate objects as inputs by extracting attributes.
            context: The context to use for validation, this is passed to functional validators.
            self_instance: An instance of a model to set attributes on from validation, this is used when running
                validation from the `__init__` method of a model.
            by_alias: Whether to use the field's alias to match the input data to an attribute.
            by_name: Whether to use the field's name to match the input data to an attribute.
        
pydantic/plugin/__init__.py