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:

```{ .python .annotate hl_lines="1  5  8-11  14-17  23-25  28" }
{!../../../docs_src/dataclasses/tutorial003.py!}
```

	// alloc on every call, so we have a clean entry to swap in.
	t := time.Now().Unix()
	e.init.Do(func() {
		e.cached.Store(&AccElem{})
		atomic.StoreInt64(&e.cachedSec, t)
	})
	acc := e.cached.Load()
	if lastT := atomic.LoadInt64(&e.cachedSec); lastT != t {
		// Check if lastT was changed by someone else.
		if atomic.CompareAndSwapInt64(&e.cachedSec, lastT, t) {
			// Now we swap in a new.
			newAcc := &AccElem{}

  }

  /**
   * Returns a plan to reuse a pooled connection, or null if the pool doesn't have a connection for
   * this address.
   *
   * If [planToReplace] is non-null, this will swap it for a pooled connection if that pooled
   * connection uses HTTP/2. That results in fewer sockets overall and thus fewer TCP slow starts.
   */
  internal fun planReusePooledConnection(

- Added full cgroup v2 swap support for both `Limited` and `Unlimited` swap.
  
  When `LimitedSwap` is enabled the swap limit would be automatically calculated for
  Burstable QoS pods. For Best-Effort/Guaranteed QoS pods, swap would be disabled.
  
  Containers with memory requests equal to their memory limits also won't have
  swap access, and it is a way to opt-out of swap for a single container.
  

func uniq(data sort.Interface) (size int) {
	p, l := 0, data.Len()
	if l <= 1 {
		return l
	}
	for i := 1; i < l; i++ {
		if !data.Less(p, i) {
			continue
		}
		p++
		if p < i {
			data.Swap(p, i)
		}
	}
	return p + 1
}

// Remove any duplicates and return unique entries.
func uniqueEntries(paths []string) []string {
	sort.Strings(paths)
	n := uniq(sort.StringSlice(paths))

				epHealth.offlineDuration = prev.offlineDuration
				epHealth.lastHCAt = prev.lastHCAt
				epHealth.latency = prev.latency
			}
			m[t.Endpoint] = epHealth
		}
	}
	// swap out the map
	sys.hc = m
	sys.hMutex.Unlock()
}

func (sys *BucketTargetSys) healthStats() map[string]epHealth {
	sys.hMutex.RLock()
	defer sys.hMutex.RUnlock()
	m := make(map[string]epHealth, len(sys.hc))

- `kubeadm`: updated warning message when swap space is detected. When swap is
  active on Linux, `kubeadm` explains that swap is supported for cgroup v2 only and
  is beta but disabled by default. ([#120198](https://github.com/kubernetes/kubernetes/pull/120198), [@pacoxu](https://github.com/pacoxu))

   * added first.
   */
  @CheckForNull
  private Listener clearListeners(@CheckForNull Listener onto) {
    // We need to
    // 1. atomically swap the listeners with TOMBSTONE, this is because addListener uses that
    //    to synchronize with us
    // 2. reverse the linked list, because despite our rather clear contract, people depend on us

corresponding type parameters have corresponding constraints.
</p>

<pre>
type Pair[A, B any] struct {
	a A
	b B
}

func (p Pair[A, B]) Swap() Pair[B, A]  { … }  // receiver declares A, B
func (p Pair[First, _]) First() First  { … }  // receiver declares First, corresponds to A in Pair
</pre>

<h2 id="Expressions">Expressions</h2>

<p>

* 🔧 Correct DeprecationWarning config and comment in pytest settings. PR [#4008](https://github.com/tiangolo/fastapi/pull/4008) by [@graingert](https://github.com/graingert).
* 🔧 Swap light/dark theme button icon. PR [#3246](https://github.com/tiangolo/fastapi/pull/3246) by [@eddsalkield](https://github.com/eddsalkield).