# Templates { #templates }

You can use any template engine you want with **FastAPI**.

A common choice is Jinja2, the same one used by Flask and other tools.

There are utilities to configure it easily that you can use directly in your **FastAPI** application (provided by Starlette).

## Install dependencies { #install-dependencies }

Make sure you create a [virtual environment](../virtual-environments.md), activate it, and install `jinja2`:

    arraycopy(contents, 0, result, 0, contents.length);
    return result;
  }

  /*
   * a "type A" unmodifiable collection freaks out proactively, even if there
   * wasn't going to be any actual work to do anyway
   */

  @Override
  public boolean addAll(Collection<? extends E> elementsToAdd) {
    throw up();
  }

  @Override

            StackOverflowError.class,
            e -> e instanceof StackOverflowError);
      }
    };

    // used under GWT, etc., since the override of this method does not exist there
    ImmutableMap<Class<? extends Throwable>, Predicate<Throwable>> exceptions() {
      return ImmutableMap.of();
    }
  }

{* ../../docs_src/middleware/tutorial001_py310.py hl[10,12:13] *}

/// tip

Here we use [`time.perf_counter()`](https://docs.python.org/3/library/time.html#time.perf_counter) instead of `time.time()` because it can be more precise for these use cases. 🤓

///

## Multiple middleware execution order { #multiple-middleware-execution-order }

   * a graph {@code T} that is a supergraph of {@code G}, augmented by, for each pair of nodes A and
   * B, an edge connecting node A to node B if there is a sequence of edges in {@code G} starting at
   * A and ending at B.
   *
   * <p>{@code strategy} defines the circumstances under which self-loops will be added to the
   * transitive closure graph.
   *

 * @since 1.0
 */
@GwtIncompatible
public class ListenableFutureTask<V extends @Nullable Object> extends FutureTask<V>
    implements ListenableFuture<V> {
  // TODO(cpovirk): explore ways of making ListenableFutureTask final. There are some valid reasons
  // such as BoundedQueueExecutorService to allow extends but it would be nice to make it final to
  // avoid unintended usage.

  // The execution list to hold our listeners.

    protected void doStop() {
      notifyFailed(new IllegalStateException("stop failure"));
    }
  }

  public void testServiceStartupTimes() {
    if (isWindows() && isJava8()) {
      // Flaky there: https://github.com/google/guava/pull/6731#issuecomment-1736298607
      return;
    }
    Service a = new NoOpDelayedService(150);
    Service b = new NoOpDelayedService(353);

	for _, v := range ahs.healStatus {
		dst[v.Endpoint] = v.toHealingDisk()
	}

	return dst
}

// getHealLocalDiskEndpoints() returns the list of disks that need
// to be healed but there is no healing routine in progress on them.
func (ahs *allHealState) getHealLocalDiskEndpoints() Endpoints {
	ahs.RLock()
	defer ahs.RUnlock()

	var endpoints Endpoints
	for ep, healing := range ahs.healLocalDisks {

    public void test_fluentBuilding() {
        final LlmChatRequest request = new LlmChatRequest().addSystemMessage("You are a helpful assistant")
                .addUserMessage("Hello!")
                .addAssistantMessage("Hi there!")
                .addUserMessage("How are you?")
                .setModel("llama3")
                .setMaxTokens(500)
                .setTemperature(0.5)
                .setStream(false);

   * that would be a problem because it violates small-test rules. Note that we strip the
   * suppression externally, but it's OK because we don't enforce test-size rules there.)
   *
   * We'd just use PackageSanityTests directly, saving us from needing this separate type, but we're
   * currently skipping MediumTests on Android, and we skip them by not making them present at