import static com.google.common.collect.testing.features.CollectionSize.ZERO;
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;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUE_QUERIES;

        return this;
    }

    /**
     * Gets the list of active features.
     *
     * @return A list of active features.
     */
    public List<String> activeFeatures() {
        return activeFeatures;
    }

    /**
     * Sets the list of active features.
     *
     * @param activeFeatures A list of active features.
     * @return This query builder.
     */

# Advanced User Guide { #advanced-user-guide }

## Additional Features { #additional-features }

The main [Tutorial - User Guide](../tutorial/index.md){.internal-link target=_blank} should be enough to give you a tour through all the main features of **FastAPI**.

In the next sections you will see other options, configurations, and additional features.

/// tip

The next sections are **not necessarily "advanced"**.

import com.google.common.collect.Multiset;
import com.google.common.collect.testing.features.Feature;
import com.google.common.collect.testing.features.TesterAnnotation;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Set;

/**
 * Optional features of classes derived from {@link Multiset}.
 *
 * @author Louis Wasserman
 */

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ADD;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.ListFeature.SUPPORTS_ADD_WITH_INDEX;

import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ITERATOR_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_REMOVE;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.features.CollectionFeature;

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;

  - redirects:
      redirect_maps:
        # Redirect all feature pages to features/*
        'caching.md': 'features/caching.md'
        'calls.md': 'features/calls.md'
        'connections.md': 'features/connections.md'
        'events.md': 'features/events.md'
        'https.md': 'features/events.md'
        'interceptors.md': 'features/interceptors.md'
        'r8_proguard.md': 'features/r8_proguard.md'

import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_PUT;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_REMOVE;