# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

 * limitations under the License.
 */
package okhttp3.internal.connection

import java.io.IOException
import okhttp3.Address
import okhttp3.HttpUrl

/**
 * Policy on choosing which connection to use for an exchange and any retries that follow. This uses
 * the following strategies:
 *
 *  1. If the current call already has a connection that can satisfy the request it is used. Using

 * prefer the simplest interface that satisfies your use case. See the <a
 * href="https://github.com/google/guava/wiki/GraphsExplained#choosing-the-right-graph-type">
 * "Choosing the right graph type"</a> section of the Guava User Guide for more details.
 *
 * <h3>Capabilities</h3>
 *
 * <p>{@code Network} supports the following use cases (<a

    /**
     * Shutdown the resource manager
     */
    public void shutdown() {
        if (shutdownInProgress) {
            return;
        }

        shutdownInProgress = true;
        log.info("Shutting down ResourceManager");

        // Cancel cleanup task
        if (cleanupTask != null) {
            cleanupTask.cancel(false);
        }

        // Force cleanup of all resources

        try {
            cleanupScheduler.awaitTermination(5, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            log.warn("Interrupted while shutting down cleanup scheduler", e);
        }

        log.info("Authentication rate limiter closed");
    }

    /**
     * Per-account attempt tracking
     */
    private static class AccountAttempts {

 * to unsigned arithmetic in all cases except:
 *
 * <ul>
 *   <li>comparisons (signed values can be negative)
 *   <li>division (avoided here)
 *   <li>shifting (right shift must be unsigned)
 * </ul>
 *
 * @author ******@****.*** (Kyle Maddison)
 * @author ******@****.*** (Geoff Pike)
 */
final class Fingerprint2011 extends AbstractNonStreamingHashFunction {

      @Nullable Comparator<? super R> rowComparator,
      @Nullable Comparator<? super C> columnComparator) {
    checkNotNull(cells);
    if (rowComparator != null || columnComparator != null) {
      /*
       * This sorting logic leads to a cellSet() ordering that may not be expected and that isn't
       * documented in the Javadoc. If a row Comparator is provided, cellSet() iterates across the

   *
   * @param code Status code as defined by
   *     [Section 7.4 of RFC 6455](http://tools.ietf.org/html/rfc6455#section-7.4).
   * @param reason Reason for shutting down, no longer than 123 bytes of UTF-8 encoded data (**not** characters) or null.
   * @throws IllegalArgumentException if [code] is invalid or [reason] is too long.
   */
  fun close(
    code: Int,

        // For direct buffers, we rely on GC
        // Could implement a more sophisticated buffer pool here
    }

    /**
     * Clean up all pooled regions
     *
     * This method should be called when shutting down to
     * release all resources.
     */
    public void cleanup() {
        // Clean up all pooled regions
        RdmaMemoryRegion region;

     * a Java library may be compatible with either the class path or the module path,
     * and the user may have provided no instruction about which type to use. In such
     * case, the plugin may apply rules for choosing a path. See for example
     * {@link JavaPathType#CLASSES} and {@link JavaPathType#MODULES}.</p>
     */
    @Nonnull
    Set<PathType> getPathTypes();