@app.post("/items/")
async def create_item(item: Item, project_id: Annotated[int, Query(...)]): ...
```

## Return Type or Response Model

When possible, include a return type. It will be used to validate, filter, document, and serialize the response.

```python
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None

/// warning | Uyarı

Yukarıdaki örnekte olduğu gibi bir `Response`'u doğrudan döndürdüğünüzde, response aynen olduğu gibi döndürülür.

Bir model ile serialize edilmez, vb.

İçinde olmasını istediğiniz veriyi taşıdığından emin olun ve değerlerin geçerli JSON olduğundan emin olun (eğer `JSONResponse` kullanıyorsanız).

///

/// note | Teknik Detaylar

import static com.google.common.collect.testing.testers.NavigableSetNavigationTester.getHoleMethods;
import static com.google.common.testing.SerializableTester.reserialize;
import static com.google.common.testing.SerializableTester.reserializeAndAssert;
import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;

  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testEmpty_serialization() {
    SortedSet<String> set = of();
    SortedSet<String> copy = SerializableTester.reserialize(set);
    assertThat(copy).isSameInstanceAs(set);
  }

  public void testSingle_comparator() {
    SortedSet<String> set = of("e");
    assertThat(set.comparator()).isEqualTo(Ordering.natural());
  }

        AtomicDouble a = new AtomicDouble(x);
        double z = a.addAndGet(y);
        assertBitEquals(x + y, z);
        assertBitEquals(x + y, a.get());
      }
    }
  }

  /** a deserialized serialized atomic holds same value */
  public void testSerialization() throws Exception {
    AtomicDouble a = new AtomicDouble();
    AtomicDouble b = serialClone(a);
    assertThat(b).isNotSameInstanceAs(a);

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.Helpers.testComparator;
import static com.google.common.testing.SerializableTester.reserialize;
import static com.google.common.testing.SerializableTester.reserializeAndAssert;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Arrays.sort;

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.Helpers.testComparator;
import static com.google.common.testing.SerializableTester.reserialize;
import static com.google.common.testing.SerializableTester.reserializeAndAssert;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Arrays.sort;

        AtomicDouble a = new AtomicDouble(x);
        double z = a.updateAndGet(value -> value - y);
        assertBitEquals(x - y, z);
        assertBitEquals(x - y, a.get());
      }
    }
  }

  /** a deserialized serialized atomic holds same value */
  public void testSerialization() throws Exception {
    AtomicDouble a = new AtomicDouble();
    AtomicDouble b = serialClone(a);
    assertThat(b).isNotSameInstanceAs(a);

  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  /*
   * This class is used to serialize ImmutableEnumSet instances.
   */
  @J2ktIncompatible // serialization
  private static final class EnumSerializedForm<E extends Enum<E>> implements Serializable {
    final EnumSet<E> delegate;

  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use EnumSerializedForm");
  }

  /*
   * This class is used to serialize ImmutableEnumMap instances.
   */
  @J2ktIncompatible // serialization
  private static final class EnumSerializedForm<K extends Enum<K>, V> implements Serializable {
    final EnumMap<K, V> delegate;