# Learn { #learn }

Here are the introductory sections and the tutorials to learn **FastAPI**.

 *
 * <pre>
 * interface Book {...}
 * public class Books {
 *   public static Book hardcover(String title) {...}
 *   public static Book paperback(String title) {...}
 * }
 * </pre>
 *
 * <p>And all the created {@code Book} instances can be tested with:
 *
 * <pre>
 * new ClassSanityTester()
 *     .forAllPublicStaticMethods(Books.class)
 *     .thatReturn(Book.class)

 *
 * <pre>
 * interface Book {...}
 * public class Books {
 *   public static Book hardcover(String title) {...}
 *   public static Book paperback(String title) {...}
 * }
 * </pre>
 *
 * <p>And all the created {@code Book} instances can be tested with:
 *
 * <pre>
 * new ClassSanityTester()
 *     .forAllPublicStaticMethods(Books.class)
 *     .thatReturn(Book.class)

}

type Author struct {
	gorm.Model
}

type Book struct {
	gorm.Model
	Author   Author
	AuthorID uint
}

func (Book) TableName() string {
	return "my_schema.a_very_very_very_very_very_very_very_very_long_table_name"
}

func TestParseConstraintNameWithSchemaQualifiedLongTableName(t *testing.T) {
	s, err := schema.Parse(
		&Book{},
		&sync.Map{},

///

For example, this custom validator checks that the item ID starts with `isbn-` for an <abbr title="ISBN means International Standard Book Number">ISBN</abbr> book number or with `imdb-` for an <abbr title="IMDB (Internet Movie Database) is a website with information about movies">IMDB</abbr> movie URL ID:

This is "synchronous" work, you are "synchronized" with the cashier/cook 👨‍🍳. You have to wait 🕙 and be there at the exact moment that the cashier/cook 👨‍🍳 finishes the burgers and gives them to you, or otherwise, someone else might take them.

<img src="/img/async/parallel-burgers/parallel-burgers-04.png" class="illustration">

			iamLogIf(ctx, err)
		}
		// No need to return errors for failed expiration of STS users
	}

	took := time.Since(purgeStart).Seconds()
	if took > maxDurationSecondsForLog {
		// Log if we took a lot of time to load.
		logger.Info("IAM expired STS purge took %.2fs", took)
	}

	// Store the newly populated map in the iam cache. This takes care of
	// removing stale entries from the existing map.

     * @param hook the validation error hook for handling errors
     * @return OptionalEntity containing the created synonym item or empty if creation failed
     */
    protected OptionalEntity<SynonymItem> createSynonymItem(final CreateForm form, final VaErrorHook hook) {
        try {
            return createSynonymItem(this, form, hook);
        } catch (final ValidationErrorException e) {

    }

    // Test hook method when MultiThreadedHttpConnectionManager class is not available
    public void test_hook_classNotFound() {
        // Create a custom hook that simulates class not found scenario
        FessCurtainFinallyHook customHook = new FessCurtainFinallyHook() {
            @Override
            public void hook(final FwAssistantDirector assistantDirector) {

This code won't be executed in your app, we only need it to *document* how that *external API* should look like.

But, you already know how to easily create automatic documentation for an API with **FastAPI**.

So we are going to use that same knowledge to document how the *external API* should look like... by creating the *path operation(s)* that the external API should implement (the ones your API will call).

/// tip