The process that happens when your API app calls the *external API* is named a "callback". Because the software that the external developer wrote sends a request to your API and then your API *calls back*, sending a request to an *external API* (that was probably created by the same developer).

import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A multiset which forwards all its method calls to another multiset. Subclasses should override
 * one or more methods to modify the behavior of the backing multiset as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

 * Observe the application's original intent. Unconcerned with OkHttp-injected headers like `If-None-Match`.
 * Permitted to short-circuit and not call `Chain.proceed()`.
 * Permitted to retry and make multiple calls to `Chain.proceed()`.
 * Can adjust Call timeouts using withConnectTimeout, withReadTimeout, withWriteTimeout.

**Network Interceptors**

 *
 * <p>An instance may be called concurrently by multiple threads to process different entries.
 * Implementations of this interface should avoid performing blocking calls or synchronizing on
 * shared resources.
 *
 * @param <K> the most general type of keys this listener can listen for; for example {@code Object}
 *     if any key is acceptable

import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * {@link FluentFuture} that forwards all calls to a delegate.
 *
 * <h3>Extension</h3>
 *
 * If you want a class like {@code FluentFuture} but with extra methods, we recommend declaring your

 * property {@code maven.ext.class.path} on the command line. As soon as dependency injection is set up, Maven
 * looks up all implementers of this interface and calls their {@link #init(Context)} method. Note:
 * Implementors are strongly advised to inherit from {@link AbstractEventSpy} instead of directly implementing this
 * interface.
 * @since 3.0.2
 */

    url = "https://github.com/bazelbuild/rules_java/releases/download/5.3.5/rules_java-5.3.5.tar.gz",
)

# Initialize the TensorFlow repository and all dependencies.
#
# The cascade of load() statements and tf_workspace?() calls works around the
# restriction that load() statements need to be at the top of .bzl files.
# E.g. we can not retrieve a new repository with http_archive and then load()
# a macro from that repository in the same file.

    // TODO: test whether null is supported (create a Feature)
    /**
     * The elements to be returned by future calls to {@code next()}, with the first at the top of
     * the stack.
     */
    final Stack<E> nextElements = new Stack<>();

    /**
     * The elements to be returned by future calls to {@code previous()}, with the first at the top
     * of the stack.
     */

     * immediately fails with the same exception:
     *
     * Thread1: calls setException(), which returns true, context switch before it can CAS
     * seenExceptions to its exception
     *
     * Thread2: calls setException(), which returns false, CASes seenExceptions to its exception,

     * improving performance for repeated calls with the same input.
     *
     * @param callback The original function to be memoized. It takes a String as input and returns a String.
     * @return A new {@code Function<String, String>} that caches the results of the original function.
     *         If the original function returns null for a given input, null will be cached and returned for subsequent calls with the same input.
     *