## Parameterize the instance

And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[9] *}

In this case, **FastAPI** won't ever touch or care about `__init__`, we will use it directly in our code.

## Create an instance

We could create an instance of this class with:

          .put(ImmutableClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build())
          .put(Comparable.class, ByToString.INSTANCE)
          .put(Comparator.class, AlwaysEqual.INSTANCE)
          .put(Ordering.class, AlwaysEqual.INSTANCE)
          .put(Range.class, Range.all())
          .put(MapDifference.class, Maps.difference(ImmutableMap.of(), ImmutableMap.of()))
          .put(

   * this parameter is marked nullable, this method does nothing.
   *
   * @param instance the instance to invoke {@code method} on, or null if {@code method} is static
   */
  public void testMethodParameter(@Nullable Object instance, Method method, int paramIndex) {
    method.setAccessible(true);
    testParameter(instance, invokable(instance, method), paramIndex, method.getDeclaringClass());
  }

  /**

      for (Invokable<?, ?> factory : getFactoriesToTest()) {
        Object instance = instantiate(factory);
        if (instance != null
            && packagesToTest.contains(Reflection.getPackageName(instance.getClass()))) {
          try {
            nullPointerTester.testAllPublicInstanceMethods(instance);
          } catch (AssertionError e) {

        try {
            Class<?> clazz = container.getContainerRealm().loadClass(PROMPTER_CLASS);
            Object instance = container.lookup(clazz);
            Method method = clazz.getMethod("prompt", String.class, List.class, String.class);
            return (String) method.invoke(instance, message, possibleValues, defaultReply);
        } catch (Exception e) {
            throw new PrompterException("Unable to call prompter", e);

      return INSTANCE;
    }

    private static final long serialVersionUID = 0;
  }

  /*
   * The implementation neither produces nor consumes any non-null instance of
   * type C, so casting the type parameter is safe.
   */
  @SuppressWarnings("unchecked")
  static <C extends Comparable> Cut<C> aboveAll() {
    return (Cut<C>) AboveAll.INSTANCE;
  }

  }

  Optional() {}

  /**
   * Returns {@code true} if this holder contains a (non-null) instance.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   */
  public abstract boolean isPresent();

  /**
   * Returns the contained instance, which must be present. If the instance might be absent, use
   * {@link #or(Object)} or {@link #orNull} instead.
   *

   * this parameter is marked nullable, this method does nothing.
   *
   * @param instance the instance to invoke {@code method} on, or null if {@code method} is static
   */
  public void testMethodParameter(
      @Nullable final Object instance, final Method method, int paramIndex) {
    method.setAccessible(true);
    testParameter(instance, invokable(instance, method), paramIndex, method.getDeclaringClass());
  }

  /**

        return singleton(name, instance, initializer, null);
    }

    public <T> StandardCrawlerContainer singleton(final String name, final T instance) {
        return singleton(name, instance, null, null);
    }

    protected static class ComponentHolder<T> {
        protected T instance;

        protected Consumer<T> destroyer;

        } catch (final Exception e) {
            throw new IllegalArgumentException("Cannot create instance of: " + clazz, e);
        } catch (final LinkageError e) {
            throw new IllegalArgumentException("Cannot create instance of: " + clazz, e);
        }
    }

    /**
     * Creates an instance of the given implementation using the given string, assumes a public string constructor.
     *