throw new UnsupportedOperationException();
    }

    @Override
    @CheckForNull
    public V merge(
        K key,
        @NonNull V value,
        BiFunction<? super @NonNull V, ? super @NonNull V, ? extends @Nullable V> function) {
      throw new UnsupportedOperationException();
    }

    @Override
    public BiMap<V, K> inverse() {

import java.util.concurrent.ConcurrentMap;
import java.util.function.BinaryOperator;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to {@link Map} instances (including instances of {@link

     * </pre>
     * @param property The property name for the message. (NotNull)
     * @param fraction The parameter fraction for message. (NotNull)
     * @param integer The parameter integer for message. (NotNull)
     * @return this. (NotNull)
     */
    public FessMessages addConstraintsDigitsMessage(String property, String fraction, String integer) {

    public static final String LABELS_LOGIN_UPDATE = "{labels.login.update}";

    /**
     * Assert the property is not null.
     * @param property The value of the property. (NotNull)
     */
    protected void assertPropertyNotNull(String property) {
        if (property == null) {
            String msg = "The argument 'property' for message should not be null.";