class MyModel(BaseModel):
    appointment_time: datetime | None
    
    @validator('appointment_time', mode='wrap')
    def validate_appointment_time(cls, v, handler):
        if v == 'now':
            return datetime.now()
        
        try:
            return handler(v)
        except ValidationError:
            # we don't want to fail, so just use None
            return None

class StrictModel(BaseModel, strict=True):
    a_string: str
    an_int: int
    set_of_ints: Set[int]


class LaxModel(BaseModel):
    lax_string: str
    strict_string1: str = Field(..., strict=True)
    strict_string2: StrictStr

class MyModel(BaseModel):
    int_or_bool: int | bool
    bool_or_int: bool | int


print(MyModel(int_or_bool=1))  #> 1, 1
print(MyModel(int_or_bool=True))  #> True, True
print(MyModel(int_or_bool='1'))  #> 1, True :-( ?

class MyModel1(BaseModel):
    none_allowed_required: str | None
    none_allowed_not_required: str | None = None

      
from typing_extentions import Required, NotRequired


class MyModel2(BaseModel):  # ... maybe, do you want this?
    none_allowed_required: Required[str]
    none_allowed_not_required: NotRequired[str]

from pydantic import validate

validate(List[int], [1, 2, '3'])  #> [1, 2, 3]

validate(List[int], [1, 2, 3], strict=True)  #> [1, 2, 3]

validate(List[int], [1, 2, '3'], strict=True)
#> raises ValidationError

class MyModel(BaseModel):
    name: str
    age: int
    friends: List[int]
    settings: Dict[str, float]

MyModel.validate_json('{...}')

from pydantic_core import SchemaValidator
schema_validator = SchemaValidator({'type': 'bool'})
print(repr(schema_validator))

SchemaValidator(name="bool", validator=BoolValidator)

print(schema_validator.validate_python(True)) -> True
print(schema_validator.validate_python(1))    -> True
print(schema_validator.validate_json('true')) -> True

from pydantic_core import SchemaValidator
# Equivalent to: Dict[str, Optional[int]]
schema_validator = SchemaValidator({
    'type': 'dict',
    'keys': {'type': 'str'},
    'values': {'type': 'optional', 'schema': {'type': 'int'}}
})

SchemaValidator(name="dict", validator=DictValidator {
    strict: false,
    key_validator: Some(StrValidator),
    value_validator: Some(
        OptionalValidator {validator: IntValidator},
    ),
    min_items: None,
    max_items: None,
    try_instance_as_dict: false,
})

class MyModel(BaseModel):
    name: str
    age: int | None = 42
    settings: dict[str, float]
    friends: list[int | str]

SchemaValidator(name="MyCoreModel", 
  validator=ModelClassValidator {
    strict: false,
    class: Py(0x12fe7e7c0), (MyCoreModel)
    new_method: Py(0x00101054130), (MyCoreModel.__new__)
    validator: ModelValidator {
        name: "Model",
        fields: [
            ModelField {
                name: "name",
                default: None,
                validator: StrValidator,
            },
            ModelField {
                name: "age",
                default: 42,
                validator: OptionalValidator { 
                  validator: IntValidator 
                },
            },
            ModelField {
                name: "settings",
                default: None,
                validator: DictValidator { ... },
            },
            ModelField {
                name: "friends",
                default: None,
                validator: ListValidator {
                    strict: false,
                    item_validator: Some(
                        UnionValidator {
                            choices: [
                                IntValidator,
                                StrValidator,
                            ],
                        },
                    ),
                    min_items: None,
                    max_items: None,
                },
            },
        ],
        extra_behavior: Ignore,
        extra_validator: None,
    },
})

#[derive(Debug, Clone)]
pub struct OptionalValidator {
    validator: Box<dyn Validator>,
}

impl OptionalValidator {
    pub const EXPECTED_TYPE: &'static str = "optional";
}

impl Validator for OptionalValidator {
    fn build(schema: &PyDict, config: Option<&PyDict>) -> PyResult<Box<dyn Validator>> {
        let schema: &PyAny = schema.get_as_req("schema")?;
        Ok(Box::new(Self {
            validator: build_validator(schema, config)?.0,
        }))
    }

    fn validate<'s, 'data>(
        &'s self,
        py: Python<'data>,
        input: &'data dyn Input,
        extra: &Extra,
    ) -> ValResult<'data, PyObject> {
        match input.is_none() {
            true => Ok(py.None()),
            false => self.validator.validate(py, input, extra),
        }
    }

    fn validate_strict<'s, 'data>(
        &'s self,
        py: Python<'data>,
        input: &'data dyn Input,
        extra: &Extra,
    ) -> ValResult<'data, PyObject> {
        match input.is_none() {
            true => Ok(py.None()),
            false => self.validator.validate_strict(py, input, extra),
        }
    }

    fn set_ref(&mut self, name: &str, validator_arc: &ValidatorArc) -> PyResult<()> {
        self.validator.set_ref(name, validator_arc)
    }

    validator_boilerplate!(Self::EXPECTED_TYPE);
}

mod optional;

...
lots of code...
...

    validator_match!(
        type_,
        dict,
        config,
        ... all the other validators
        // unions
        self::union::UnionValidator,
        self::optional::OptionalValidator,
        ...
    )