/// note | Technical Details

`Header` is a "sister" class of `Path`, `Query` and `Cookie`. It also inherits from the same common `Param` class.

But remember that when you import `Query`, `Path`, `Header`, and others from `fastapi`, those are actually functions that return special classes.

///

/// info

To declare headers, you need to use `Header`, because otherwise the parameters would be interpreted as query parameters.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

As part of the application object creation, a *path operation* for `/openapi.json` (or for whatever you set your `openapi_url`) is registered.

It just returns a JSON response with the result of the application's `.openapi()` method.

    <version>4.1.0-SNAPSHOT</version>
  </parent>

  <artifactId>maven-api</artifactId>
  <packaging>pom</packaging>
  <name>Maven 4 API</name>
  <description>A new immutable API for Maven 4 to better manage what plugins and extensions can influence.</description>

  <modules>
    <module>maven-api-annotations</module>
    <module>maven-api-di</module>
    <module>maven-api-xml</module>
    <module>maven-api-model</module>

* «the performance»: NOT «die Performance»
* «the query»: «die Query»
* «the recap»: «die Zusammenfassung»
* «the request» (what the client sends to the server): «der Request»
* «the request body»: «der Requestbody»
* «the request bodies» (plural): «die Requestbodys»
* «the response» (what the server sends back to the client): «die Response»
* «the return type»: «der Rückgabetyp»
* «the return value»: «der Rückgabewert»

### Required, can be `None` { #required-can-be-none }

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but simply do not declare a default value:

{* ../../docs_src/query_params_str_validations/tutorial006c_an_py310.py hl[9] *}

* `feature`: Features
    * New features, adding support for things that didn't exist before.
* `bug`: Fixes

            // Do NOT call setRootLoggerLevel - this is the fix!
        }

        // Verify that setRootLoggerLevel was not called
        assertEquals(0, slf4jConfiguration.setRootLoggerLevelCallCount);

        // Verify that system property was not set
        assertNull(System.getProperty(Constants.MAVEN_LOGGER_DEFAULT_LOG_LEVEL));
    }

    @Test

  //   spinning, so we use SPIN_THRESHOLD_NANOS which is what AbstractQueuedSynchronizer uses for
  //   similar purposes.
  // * We want to behave reasonably for timeouts of 0
  // * We are more responsive to completion than timeouts. This is because parkNanos depends on
  //   system scheduling and as such we could either miss our deadline, or unpark() could be delayed

  // Selects TLSv1.3 so we are specific about our intended version ranges (not just 1.3)
  // and because it's a common pattern for VMs to have differences between supported and
  // defaulted versions for TLS based on what is requested.
  override fun newSSLContext(): SSLContext = SSLContext.getInstance("TLSv1.3", provider)

  override fun platformTrustManager(): X509TrustManager {
    val factory =
      TrustManagerFactory.getInstance(

        // By default, test fixtures compile to the same JVM version as the production code.
        targetJvmVersion = compilations.named("main").flatMap { it.targetJvmVersion }
    }
}

// The below mimics what the java-library plugin does, but creating a library of test fixtures instead.

sourceSets.matching { it.name.endsWith("Test") }.all {