```

////

`OAuth2PasswordRequestForm` is a class dependency that declares a form body with:

* The `username`.
* The `password`.
* An optional `scope` field as a big string, composed of strings separated by spaces.
* An optional `grant_type`.

/// tip

The OAuth2 spec actually *requires* a field `grant_type` with a fixed value of `password`, but `OAuth2PasswordRequestForm` doesn't enforce it.

 * This information include the dependency type (main classes, test classes, <i>etc.</i>),
 * a scope (compile-time, run-time <i>etc.</i>), an obligation (whether the dependency
 * is optional or mandatory), and possible exclusions for transitive dependencies.
 * The {@linkplain #getVersionConstraint() version} and the {@linkplain #getOptional() obligation}
 * may not be defined precisely.
 *
 * @since 4.0.0
 */

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.api.services;

import java.util.List;
import java.util.Map;
import java.util.Optional;

import org.apache.maven.api.Service;
import org.apache.maven.api.Session;
import org.apache.maven.api.Toolchain;
import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;

            </Export-Package>
            <Import-Package>
              com.google.common.util.concurrent.internal,
              javax.annotation;resolution:=optional,
              javax.crypto.*;resolution:=optional,
              sun.misc.*;resolution:=optional
            </Import-Package>
            <Bundle-DocURL>https://github.com/google/guava/</Bundle-DocURL>
          </instructions>
        </configuration>

    *  `dict` değişkeninin `value` değeri `float` tipindedir (lherbir item'ın "price" değeri).

#### `Optional`

`Optional` bir değişkenin `str`gibi bir tipi olabileceğini ama isteğe bağlı olarak tipinin `None` olabileceğini belirtir:

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

            """
        ),
    ],
    include: Annotated[
        Optional[IncEx],
        Doc(
            """
            Pydantic's `include` parameter, passed to Pydantic models to set the
            fields to include.
            """
        ),
    ] = None,
    exclude: Annotated[
        Optional[IncEx],
        Doc(
            """

from typing import List, Optional

from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel

from .utils import PYDANTIC_V2, needs_pydanticv2


class SubItem(BaseModel):
    subname: str
    sub_description: Optional[str] = None
    tags: List[str] = []
    if PYDANTIC_V2:
        model_config = {"json_schema_serialization_defaults_required": True}


class Item(BaseModel):

from pydantic import BaseModel
from typing import Optional

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: bool = Optional[None]


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Optional[str] = None):
    return {"item_id": item_id, "q": q}

@item_router.get("/")
def get_items(user_id: Optional[str] = None):
    if user_id is None:
        return [{"item_id": "i1", "user_id": "u1"}, {"item_id": "i2", "user_id": "u2"}]
    else:
        return [{"item_id": "i2", "user_id": user_id}]


@item_router.get("/{item_id}")
def get_item(item_id: str, user_id: Optional[str] = None):
    if user_id is None:
        return {"item_id": item_id}
    else:

                    packages.addAll(descriptor.getExportedPackages());
                }
            }
        } catch (IOException ignored) {
            // exports descriptors are entirely optional
        }

        return new CoreExtensionEntry(loader, artifacts, packages, null, null);
    }

    public static CoreExtensionEntry discoverFrom(