It's still possible to use `BackgroundTask` alone in FastAPI, but you have to create the object in your code and return a Starlette `Response` including it.

 *
 * <p><b>Warning:</b> The methods of {@code ForwardingMap} forward <i>indiscriminately</i> to the
 * methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change the
 * behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should
 * override {@code putAll} as well, either providing your own implementation, or delegating to the

 *
 * <p><b>Warning:</b> The methods of {@code ForwardingMap} forward <i>indiscriminately</i> to the
 * methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change the
 * behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should
 * override {@code putAll} as well, either providing your own implementation, or delegating to the

 *
 * <p><b>Warning:</b> The methods of {@code ForwardingSortedMultiset} forward
 * <b>indiscriminately</b> to the methods of the delegate. For example, overriding {@link
 * #add(Object, int)} alone <b>will not</b> change the behavior of {@link #add(Object)}, which can
 * lead to unexpected behavior. In this case, you should override {@code add(Object)} as well,

      use, offer to sell, sell, import, and otherwise transfer the Work,
      where such license applies only to those patent claims licensable
      by such Contributor that are necessarily infringed by their
      Contribution(s) alone or by combination of their Contribution(s)
      with the Work to which such Contribution(s) was submitted. If You
      institute patent litigation against any entity (including a

  public void testBuilderReuse() {
    Builder<String, Integer> builder = new Builder<>();
    ImmutableMap<String, Integer> mapOne = builder.put("one", 1).put("two", 2).buildOrThrow();
    ImmutableMap<String, Integer> mapTwo = builder.put("three", 3).put("four", 4).buildOrThrow();

    assertMapEquals(mapOne, "one", 1, "two", 2);
    assertMapEquals(mapTwo, "one", 1, "two", 2, "three", 3, "four", 4);
  }

                }
            }
        }

        if (dr == null && path != null) {
            /* We did not match a domain based root. Now try to match the
             * longest path in the list of stand-alone referrals.
             */
            if (referrals != null && now > referrals.expiration) {
                referrals = null;
            }
            if (referrals == null) {

      use, offer to sell, sell, import, and otherwise transfer the Work,
      where such license applies only to those patent claims licensable
      by such Contributor that are necessarily infringed by their
      Contribution(s) alone or by combination of their Contribution(s)
      with the Work to which such Contribution(s) was submitted. If You
      institute patent litigation against any entity (including a

      use, offer to sell, sell, import, and otherwise transfer the Work,
      where such license applies only to those patent claims licensable
      by such Contributor that are necessarily infringed by their
      Contribution(s) alone or by combination of their Contribution(s)
      with the Work to which such Contribution(s) was submitted. If You
      institute patent litigation against any entity (including a

      use, offer to sell, sell, import, and otherwise transfer the Work,
      where such license applies only to those patent claims licensable
      by such Contributor that are necessarily infringed by their
      Contribution(s) alone or by combination of their Contribution(s)
      with the Work to which such Contribution(s) was submitted. If You
      institute patent litigation against any entity (including a