assertEquals(a, sortedMultiset.pollLastEntry());
    assertTrue(sortedMultiset.isEmpty());
  }

  @CollectionSize.Require(SEVERAL)
  public void testFirst() {
    assertEquals(a, sortedMultiset.firstEntry());
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(SEVERAL)
  public void testPollFirst() {
    assertEquals(a, sortedMultiset.pollFirstEntry());

import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.google.MultisetFeature.ENTRIES_ARE_VIEWS;
import static java.util.Collections.singleton;

Here's a little bit of that history.

## Alternatives { #alternatives }

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEY_QUERIES;

  }

  @CollectionSize.Require(SEVERAL)
  public void testLowerHole() {
    resetWithHole();
    assertEquals(null, navigableSet.lower(a));
    assertEquals(a, navigableSet.lower(b));
    assertEquals(a, navigableSet.lower(c));
  }

  @CollectionSize.Require(SEVERAL)
  public void testFloorHole() {
    resetWithHole();

import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static java.util.Arrays.asList;

import com.google.common.annotations.GwtCompatible;

    assertEquals(a, sortedMultiset.pollLastEntry());
    assertTrue(sortedMultiset.isEmpty());
  }

  @CollectionSize.Require(SEVERAL)
  public void testFirst() {
    assertEquals(a, sortedMultiset.firstEntry());
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(SEVERAL)
  public void testPollFirst() {
    assertEquals(a, sortedMultiset.pollFirstEntry());

  }

  @CollectionSize.Require(SEVERAL)
  public void testLowerHole() {
    resetWithHole();
    assertEquals(null, navigableSet.lower(a));
    assertEquals(a, navigableSet.lower(b));
    assertEquals(a, navigableSet.lower(c));
  }

  @CollectionSize.Require(SEVERAL)
  public void testFloorHole() {
    resetWithHole();

import static com.google.common.collect.testing.Helpers.mapEntry;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ITERATOR_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;

## OAuth2 { #oauth2 }

OAuth2 is a specification that defines several ways to handle authentication and authorization.

It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".