///

### Bước 2: Tạo một `FastAPI` "instance"

```Python hl_lines="3"
{!../../docs_src/first_steps/tutorial001.py!}
```

Biến `app` này là một "instance" của class `FastAPI`.

Đây sẽ là điểm cốt lõi để tạo ra tất cả API của bạn.

`app` này chính là điều được nhắc tới bởi `uvicorn` trong câu lệnh:

  private final Stats yStats;
  private final double sumOfProductsOfDeltas;

  /**
   * Internal constructor. Users should use {@link PairedStatsAccumulator#snapshot}.
   *
   * <p>To ensure that the created instance obeys its contract, the parameters should satisfy the
   * following constraints. This is the callers responsibility and is not enforced here.
   *
   * <ul>

  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**
   * Creates a <i>mutable</i> {@code CompactHashSet} instance containing the elements of the given
   * collection in unspecified order.
   *

 *       allocating garbage).
 * </ul>
 *
 * <p>Disadvantages compared to {@code long[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).

 *       allocating garbage).
 * </ul>
 *
 * <p>Disadvantages compared to {@code int[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).

  }

  public void testToMap_nullKey() {
    assertThrows(
        NullPointerException.class, () -> fluent(1, null, 2).toMap(Functions.constant("foo")));
  }

  public void testToMap_nullValue() {
    assertThrows(NullPointerException.class, () -> fluent(1, 2, 3).toMap(Functions.constant(null)));
  }

  public void testIndex() {
    ImmutableListMultimap<Integer, String> expected =

- Deprecate the instance type beta label (`beta.kubernetes.io/instance-type`) in favor of its GA equivalent: `node.kubernetes.io/instance-type` ([#82049](https://github.com/kubernetes/kubernetes/pull/82049), [@andrewsykim](https://github.com/andrewsykim))

## **2. Prerequisites**

- Install Hortonworks Distribution using this [guide.](https://docs.hortonworks.com/HDPDocuments/Ambari-2.7.1.0/bk_ambari-installation/content/ch_Installing_Ambari.html)

## Prerequisites

Install Dex by following [Dex Getting Started Guide](https://dexidp.io/docs/getting-started/)

### Start Dex

```
~ ./bin/dex serve dex.yaml
time="2020-07-12T20:45:50Z" level=info msg="config issuer: http://127.0.0.1:5556/dex"

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import junit.framework.TestCase;

/**
 * Unit tests for {@link ExecutionList}.
 *
 * @author Nishant Thakkar
 * @author Sven Mawson
 */
public class ExecutionListTest extends TestCase {

  private final ExecutionList list = new ExecutionList();

  public void testRunOnPopulatedList() throws Exception {