* least old versions), so we mostly do. This is useful because we don't actually run our CI on
     * Windows under Java 8, at least as of this writing.
     *
     * Under Windows in particular, we want to test that:
     *
     * - Under Java 9+, createTempDir() succeeds because it can look up the *real* username, rather
     * than relying on the one from the system property.
     *

  {{.HelpName}} {{if .VisibleFlags}}[FLAGS] {{end}}DIR{1...64}
  {{.HelpName}} {{if .VisibleFlags}}[FLAGS] {{end}}DIR{1...64} DIR{65...128}

DIR:
  DIR points to a directory on a filesystem. When you want to combine
  multiple drives into a single large system, pass one directory per
  filesystem separated by space. You may also use a '...' convention
  to abbreviate the directory arguments. Remote directories in a

# 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

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and install `jinja2`:

<div class="termy">

      try {
        Method unused = clazz.getDeclaredMethod("writeReplace");
        continue; // It overrides writeReplace, so it's safe.
      } catch (NoSuchMethodException e) {
        // This is a class whose supertypes we want to examine. We'll do that below.
      }
      Optional<Class<?>> supersWithPackagePrivateWriteReplace =
          FluentIterable.from(TypeToken.of(clazz).getTypes())
              .transform(TypeToken::getRawType)

 *   <li>We need to be careful about how we suppress {@code suite()} methods in {@code common.io}.
 *       The generated suite for {@code FooTest} ends up containing {@code FooTest} itself plus some
 *       other tests. We want to exclude the other tests (which Android can't handle) while
 *       continuing to run {@code FooTest} itself. This is exactly what happens with {@code

```console
$ pip install "fastapi[standard]"

---> 100%
```

</div>

/// note

When you install with `pip install "fastapi[standard]"` it comes with some default optional standard dependencies.

If you don't want to have those optional dependencies, you can instead install `pip install fastapi`.

///

## Advanced User Guide

There is also an **Advanced User Guide** that you can read later after this **Tutorial - User guide**.

      try {
        Method unused = clazz.getDeclaredMethod("writeReplace");
        continue; // It overrides writeReplace, so it's safe.
      } catch (NoSuchMethodException e) {
        // This is a class whose supertypes we want to examine. We'll do that below.
      }
      Optional<Class<?>> supersWithPackagePrivateWriteReplace =
          FluentIterable.from(TypeToken.of(clazz).getTypes())
              .transform(TypeToken::getRawType)

We'll explain everything via an example. Let's say you make some changes on your branch `myTestBranch`
(we highly recommend to name this branch without prefix and hyphen (`-`) because it's used to generate build type ID) and want to
test these changes without affecting `master`/`release` pipeline. Here are the instructions.

      BaseEncoding encoding, String cannotDecode, @Nullable String expectedMessage) {
    // We use this somewhat weird pattern with an enum for each assertion we want to make as a way
    // of dealing with the fact that one of the assertions is @GwtIncompatible but we don't want to
    // have to have duplicate @GwtIncompatible test methods just to make that assertion.

      @CheckForNull Type ownerType, Class<?> rawType, Type... arguments) {
    if (ownerType == null) {
      return newParameterizedType(rawType, arguments);
    }
    // ParameterizedTypeImpl constructor already checks, but we want to throw NPE before IAE
    checkNotNull(arguments);
    checkArgument(rawType.getEnclosingClass() != null, "Owner type for unenclosed %s", rawType);
    return new ParameterizedTypeImpl(ownerType, rawType, arguments);
  }