*  XPath namespace prefixes are resolved from the namespaceNode.
     *  The implementation of this is a little slow, since it creates
     *  a number of objects each time it is called.  This could be optimized
     *  to keep the same objects around, but then thread-safety issues would arise.
     *
     *  @param contextNode The node to start searching from.
     *  @param expression A valid XPath string.

        .Builder()
        .add("Connection", "close")
        .add("Transfer-Encoding", "chunked")
        .build()
    val headers2 =
      Headers
        .Builder()
        .add("Connection", "keep-alive")
        .add("Transfer-Encoding", "chunked")
        .build()
    assertThat(headers2).isNotEqualTo(headers1)
    assertThat(headers2.hashCode()).isNotEqualTo(headers1.hashCode().toLong())
  }

	wrappedHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// If server is in shutdown.
		if atomic.LoadUint32(&srv.inShutdown) != 0 {
			// To indicate disable keep-alive, server is shutting down.
			w.Header().Set("Connection", "close")

			// Add 1 minute retry header, incase-client wants to honor it
			w.Header().Set(RetryAfter, "60")

But when checking benchmarks and comparisons you should keep the following in mind.

## Benchmarks and speed { #benchmarks-and-speed }

When you check the benchmarks, it is common to see several tools of different types compared as equivalent.

/**
 * Manages reuse of HTTP and HTTP/2 connections for reduced network latency. HTTP requests that
 * share the same [Address] may share a [Connection]. This class implements the policy
 * of which connections to keep open for future use.
 *
 * @constructor Create a new connection pool with tuning parameters appropriate for a single-user
 * application. The tuning parameters in this pool are subject to change in future OkHttp releases.

            // xapth.<field>=<value>
        }

        // config.*
        public static class Config {
            public static final String KEEP_ORIGINAL_BODY = "keep.original.body";
            public static final String CLEANUP_ALL = "cleanup.all";
            public static final String CLEANUP_URL_FILTERS = "cleanup.urlFilters";
            public static final String JCIFS_PREFIX = "jcifs.";

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

   * example, we could compute the appropriate throttle time for an incoming request, and make the
   * calling thread wait for that time.
   *
   * The simplest way to maintain a rate of QPS is to keep the timestamp of the last granted
   * request, and ensure that (1/QPS) seconds have elapsed since then. For example, for a rate of
   * QPS=5 (5 tokens per second), if we ensure that a request isn't granted earlier than 200ms after

Let's continue from the previous example. We wanted to **annotate the function with one type**, but we wanted to be able to return from the function something that actually includes **more data**.

We want FastAPI to keep **filtering** the data using the response model. So that even though the function returns more data, the response will only include the fields declared in the response model.

OkHttp depends on [Okio][okio] for high-performance I/O and the [Kotlin standard library][kotlin]. Both are small libraries with strong backward-compatibility.

We highly recommend you keep OkHttp up-to-date. As with auto-updating web browsers, staying current
with HTTPS clients is an important defense against potential security problems. [We