*       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked
   *       that when equal parameters are passed, the result instance should also be equal; and vice
   *       versa.
   *   <li>If a non-private constructor or non-private static factory method exists:
   *       <ul>
   *         <li>Test will fail if default value for a parameter cannot be determined.

   *       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked
   *       that when equal parameters are passed, the result instance should also be equal; and vice
   *       versa.
   *   <li>If a non-private constructor or non-private static factory method exists:
   *       <ul>
   *         <li>Test will fail if default value for a parameter cannot be determined.

            .withTearDown(parentBuilder.getTearDown())
            .createTestSuite());
    /*
     * TODO(cpovirk): the Map tests duplicate most of this effort by using a
     * CollectionTestSuiteBuilder on values(). It would be nice to avoid that
     */
    derived.add(
        SetTestSuiteBuilder.using(
                new BiMapValueSetGenerator<K, V>(parentBuilder.getSubjectGenerator()))

 * it delegates to other components that potentially encounter problems. Then, the problem reporter can focus on
 * providing a simple error message, leaving the donkey work of creating a nice model problem to this component.
 *
 */
class DefaultModelProblemCollector implements ModelProblemCollector {

    private final ModelBuilderResult result;

    private List<ModelProblem> problems;

   * <i>adding</i> to the returned set is not possible.
   */
  @Override
  public Set<K> keySet() {
    return super.keySet();
  }

  /**
   * Returns a collection of all values in the multimap. Changes to the returned collection will
   * update the underlying multimap, and vice versa.
   *

       * need to clear our reference to the TimeoutFuture is the reason we use a *static* nested
       * class with a manual reference back to the "containing" class.)
       *
       * This has the nice-ish side effect of limiting reentrancy: run() calls
       * timeoutFuture.setException() calls run(). That reentrancy would already be harmless, since

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

    So, you might still need to use Pydantic models.

    But if you have a bunch of dataclasses laying around, this is a nice trick to use them to power a web API using FastAPI. 🤓

## Dataclasses in `response_model`

You can also use `dataclasses` in the `response_model` parameter:

```Python hl_lines="1  7-13  19"

   * `new Integer` (as we do) instead of `Integer.valueOf`. However, under J2KT, `new Integer`
   * gets translated back to `Integer.valueOf` because that is the only thing J2KT can support. And
   * anyway, it's nice to avoid `Integer.valueOf` because the Android toolchain optimizes multiple
   * `Integer.valueOf` calls into one! So we stick with the deprecated `Integer` constructor.
   */

  public void testEqualsEquivalent() {

            .withTearDown(parentBuilder.getTearDown())
            .createTestSuite());
    /*
     * TODO(cpovirk): the Map tests duplicate most of this effort by using a
     * CollectionTestSuiteBuilder on values(). It would be nice to avoid that
     */
    derived.add(
        SetTestSuiteBuilder.using(
                new BiMapValueSetGenerator<K, V>(parentBuilder.getSubjectGenerator()))

   * `new Integer` (as we do) instead of `Integer.valueOf`. However, under J2KT, `new Integer`
   * gets translated back to `Integer.valueOf` because that is the only thing J2KT can support. And
   * anyway, it's nice to avoid `Integer.valueOf` because the Android toolchain optimizes multiple
   * `Integer.valueOf` calls into one! So we stick with the deprecated `Integer` constructor.
   */

  public void testEqualsEquivalent() {