}
        }, "Multiple close operations should not cause issues");

        // Verify iterator still works after multiple closes
        assertFalse(emptyIterator.hasNext(), "Iterator should still work after multiple closes");
        assertNull(emptyIterator.next(), "Iterator should still return null after multiple closes");
    }

    @Test

        // Test additional acquire
        session.acquire();
        assertTrue(session.isInUse(), "Session should still be in use after additional acquire");

        // Test release (still in use because of initial transport acquire)
        session.release();
        assertTrue(session.isInUse(), "Session should still be in use after one release");

        // Test final release
        session.release();

In some cases, you might still have to use Pydantic's version of `dataclasses`. For example, if you have errors with the automatically generated API documentation.

In that case, you can simply swap the standard `dataclasses` with `pydantic.dataclasses`, which is a drop-in replacement:

{* ../../docs_src/dataclasses/tutorial003.py hl[1,5,8:11,14:17,23:25,28] *}

1. We still import `field` from standard `dataclasses`.

            // Execute
            TimeZone result = newProvider.getRequestedTimeZone(requestManager);

            // Verify that the provider still returns the static centralTimeZone
            assertNotNull(result);
            assertEquals(FessUserTimeZoneProcessProvider.centralTimeZone, result);
            assertNotSame(newTimeZone, result);
        } finally {

**FastAPI** is already being used in production in many applications and systems. And the test coverage is kept at 100%. But its development is still moving quickly.

New features are added frequently, bugs are fixed regularly, and the code is still continuously improving.

        request.addHeader("Host", "example.com");
        key = virtualHostHelper.getVirtualHostKey();
        assertEquals("", key); // Still empty due to caching

        // Test caching by calling again - should return cached value
        key = virtualHostHelper.getVirtualHostKey();
        assertEquals("", key); // Still cached value
    }

    public void test_getVirtualHostKey_withCaching() {

## Why is Erasure Code useful?

{* ../../docs_src/query_params_str_validations/tutorial002_an_py310.py hl[9] *}

Notice that the default value is still `None`, so the parameter is still optional.

But now, having `Query(max_length=50)` inside of `Annotated`, we are telling FastAPI that we want it to have **additional validation** for this value, we want it to have maximum 50 characters. 😎

/// tip

But it is still recommended to use the ideas above, using multiple classes, instead of these parameters.

This is because the JSON Schema generated in your app's OpenAPI (and the docs) will still be the one for the complete model, even if you use `response_model_include` or `response_model_exclude` to omit some attributes.

Hiding your documentation user interfaces in production *shouldn't* be the way to protect your API.

That doesn't add any extra security to your API, the *path operations* will still be available where they are.

If there's a security flaw in your code, it will still exist.