### Development Workflow
1. **Fork** the repository on GitHub
2. **Create** your feature branch: `git checkout -b feature/amazing-feature`
3. **Follow** the coding standards: `mvn formatter:format`
4. **Add** comprehensive tests for new functionality
5. **Commit** your changes: `git commit -m 'Add amazing feature'`
6. **Push** to the branch: `git push origin feature/amazing-feature`
7. **Submit** a Pull Request with detailed description

import com.google.common.collect.Multimap;
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 {@code Multimap}.
 *
 * @author Louis Wasserman
 */

  private final Set<Feature<? super List>> implied;

  ListFeature(Feature<? super List>... implied) {
    this.implied = copyToSet(implied);
  }

  @Override
  public Set<Feature<? super List>> getImpliedFeatures() {
    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {

    @Override
    public Iterable<E> order(List<E> insertionOrder) {
      return gen.order(insertionOrder);
    }
  }

  private static Set<Feature<?>> computeReserializedCollectionFeatures(Set<Feature<?>> features) {
    Set<Feature<?>> derivedFeatures = new HashSet<>(features);
    derivedFeatures.remove(SERIALIZABLE);
    derivedFeatures.remove(SERIALIZABLE_INCLUDING_VIEWS);
    return derivedFeatures;
  }

import static com.google.common.collect.testing.features.FeatureUtil.addImpliedFeatures;
import static java.util.Arrays.asList;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.features.Feature;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

        propertyMap.put(key, value);
    }

    /**
     * Gets the map of parser features.
     *
     * @return the feature map
     */
    public Map<String, String> getFeatureMap() {
        return featureMap;
    }

    /**
     * Sets the map of parser features.
     *
     * @param featureMap the feature map to set
     */
    public void setFeatureMap(final Map<String, String> featureMap) {

Each file is a list of API features, one per line.

go1.txt (and similarly named files) are frozen once a version has been
shipped. Each file adds new lines but does not remove any.

except.txt lists features that may disappear without breaking true
compatibility.

Starting with go1.19.txt, each API feature line must end in "#nnnnn"

        just a feature that seems like a sensible addition to Guava?


        Before new features get added to Guava, we really want to be sure that it's for a use case
        that actually comes up in the real world. We want to hear the real-world use case so the
        community can discuss and debate whether this feature is actually the *best* way to address

@GwtCompatible
public enum SetFeature implements Feature<Set> {
  GENERAL_PURPOSE(CollectionFeature.GENERAL_PURPOSE);

  private final Set<Feature<? super Set>> implied;

  SetFeature(Feature<? super Set>... implied) {
    this.implied = copyToSet(implied);
  }

  @Override
  public Set<Feature<? super Set>> getImpliedFeatures() {
    return implied;
  }

          annotationClass.getDeclaringClass(),
          returnType.getComponentType());
    }
  }

  // This is public so that tests for Feature enums we haven't yet imagined
  // can reuse it.
  public static <E extends Enum<?> & Feature<?>> void assertGoodFeatureEnum(
      Class<E> featureEnumClass) {
    Class<?>[] classes = featureEnumClass.getDeclaredClasses();
    for (Class<?> containedClass : classes) {