И `Field` (из Pydantic) также возвращает экземпляр `FieldInfo`.

`Body` также напрямую возвращает объекты подкласса `FieldInfo`. И есть и другие, с которыми вы познакомитесь позже, которые являются подклассами класса `Body`.

    GetJsonSchemaHandler as GetJsonSchemaHandler,
)
from pydantic._internal._typing_extra import eval_type_lenient
from pydantic._internal._utils import lenient_issubclass as lenient_issubclass
from pydantic.fields import FieldInfo as FieldInfo
from pydantic.json_schema import GenerateJsonSchema as GenerateJsonSchema
from pydantic.json_schema import JsonSchemaValue as JsonSchemaValue
from pydantic_core import CoreSchema as CoreSchema

from fastapi.testclient import TestClient
from pydantic import BaseModel, ConfigDict
from pydantic.fields import FieldInfo

from .utils import needs_py310


def test_model_field_default_required():
    from fastapi._compat import v2

    # For coverage
    field_info = FieldInfo(annotation=str)
    field = v2.ModelField(name="foo", field_info=field_info)
    assert field.default is Undefined

Na realidade, `Query`, `Path` e outros que você verá em seguida, criam objetos de subclasses de uma classe `Param` comum, que é ela mesma uma subclasse da classe `FieldInfo` do Pydantic.

E `Field` do Pydantic retorna uma instância de `FieldInfo` também.

`Body` também retorna objetos de uma subclasse de `FieldInfo` diretamente. E tem outras que você verá mais tarde que são subclasses da classe `Body`.

En realidad, `Query`, `Path` y otros que verás a continuación crean objetos de subclases de una clase común `Param`, que es a su vez una subclase de la clase `FieldInfo` de Pydantic.

Y `Field` de Pydantic también regresa una instance de `FieldInfo`.

`Body` también devuelve objetos de una subclase de `FieldInfo` directamente. Y hay otros que verás más adelante que son subclases de la clase `Body`.

)
from fastapi.datastructures import DefaultPlaceholder, DefaultType
from fastapi.exceptions import FastAPIDeprecationWarning, PydanticV1NotSupportedError
from pydantic import BaseModel
from pydantic.fields import FieldInfo
from typing_extensions import Literal

from ._compat import v2

if TYPE_CHECKING:  # pragma: nocover
    from .routing import APIRoute

# Cache for `create_cloned_field`

        ]
        if fastapi_specific_annotations:
            fastapi_annotation: Union[FieldInfo, params.Depends, None] = (
                fastapi_specific_annotations[-1]
            )
        else:
            fastapi_annotation = None
        # Set default for Annotated FieldInfo
        if isinstance(fastapi_annotation, FieldInfo):
            # Copy `field_info` because we mutate `field_info.default` below.

from pydantic import AliasChoices, AliasPath
from pydantic.fields import FieldInfo
from typing_extensions import Literal, deprecated

from ._compat import (
    Undefined,
)

_Unset: Any = Undefined


class ParamTypes(Enum):
    query = "query"
    header = "header"
    path = "path"
    cookie = "cookie"


class Param(FieldInfo):  # type: ignore[misc]
    in_: ParamTypes

    def __init__(