{* ../../docs_src/first_steps/tutorial001.py hl[1] *}

`FastAPI` is a Python class that provides all the functionality for your API.

/// note | Technical Details

`FastAPI` is a class that inherits directly from `Starlette`.

You can use all the <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a> functionality with `FastAPI` too.

///

    implements Serializable {

  /**
   * Creates a new, empty multiset, sorted according to the elements' natural order. All elements
   * inserted into the multiset must implement the {@code Comparable} interface. Furthermore, all
   * such elements must be <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a

020B          ; valid                                  # 1.1  LATIN SMALL LETTER I WITH INVERTED BREVE
020C          ; mapped                 ; 020D          # 1.1  LATIN CAPITAL LETTER O WITH DOUBLE GRAVE
020D          ; valid                                  # 1.1  LATIN SMALL LETTER O WITH DOUBLE GRAVE
020E          ; mapped                 ; 020F          # 1.1  LATIN CAPITAL LETTER O WITH INVERTED BREVE

   *       be checked to be equal to the instance before serialization.
   *   <li>If {@code C} doesn't explicitly implement {@code equals} but instead inherits it from a
   *       superclass, no equality check is done on the deserialized instance because it's not clear
   *       whether the author intended for the class to be a value type.

			t.Fatalf("Test %d: %s: Failed parsing response body: <ERROR> %v", i+1, instanceType, err)
		}

		if recV4.Code != testCase.expectedRespStatus {
			// Verify whether the bucket policy fetched is same as the one inserted.
			var expectedPolicy *policy.BucketPolicy
			expectedPolicy, err = policy.ParseBucketPolicyConfig(strings.NewReader(expectedBucketPolicyStr), testCase.bucketName)
			if err != nil {

 * provided {@code standardPutAll} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingNavigableMap}.
 *

 * provided {@code standardPutAll} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingNavigableMap}.
 *

### Type Annotations and Tooling { #type-annotations-and-tooling }

First let's see how editors, mypy and other tools would see this.

`BaseUser` has the base fields. Then `UserIn` inherits from `BaseUser` and adds the `password` field, so, it will include all the fields from both models.

We annotate the function return type as `BaseUser`, but we are actually returning a `UserIn` instance.

        // When & Then
        assertThrows(ArrayIndexOutOfBoundsException.class, () -> {
            req.encode(smallBuffer, 0);
        });
    }

    @Test
    @DisplayName("Should correctly inherit from ServerMessageBlock2Request")
    void testInheritance() {
        // Then
        assertTrue(request instanceof ServerMessageBlock2Request);
        assertTrue(request instanceof ServerMessageBlock2);
    }

///

### `Response` { #response }

The main `Response` class, all the other responses inherit from it.

You can return it directly.

It accepts the following parameters:

* `content` - A `str` or `bytes`.
* `status_code` - An `int` HTTP status code.
* `headers` - A `dict` of strings.