* @param propertyKey The key of the property. (NotNull)
     * @return The value of found property. (NotNull: if not found, exception)
     * @throws ConfigPropertyNotFoundException When the property is not found.
     */
    String get(String propertyKey);

    /**
     * Is the property true?
     * @param propertyKey The key of the property which is boolean type. (NotNull)

     * @param propertyKey The key of the property. (NotNull)
     * @return The value of found property. (NotNull: if not found, exception)
     * @throws ConfigPropertyNotFoundException When the property is not found.
     */
    String get(String propertyKey);

    /**
     * Is the property true?
     * @param propertyKey The key of the property which is boolean type. (NotNull)

    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.";

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Collection;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to object arrays.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Collection;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to object arrays.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible

        String[] values = null;
        if (input instanceof String[]) {
            values = (String[]) input;
        } else if (input instanceof List) {
            values = ((List<?>) input).stream().filter(Objects::nonNull).map(Object::toString).toArray(n -> new String[n]);
        } else if (input instanceof String) {
            return input.toString();
        }
        if (values != null) {

          Collection<V> valueCollection = keyToValueCollectionEntry.getValue();
          return CollectSpliterators.map(
              valueCollection.spliterator(),
              Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.IMMUTABLE,
              (V value) -> immutableEntry(key, value));
        },
        Spliterator.SIZED | (this instanceof SetMultimap ? Spliterator.DISTINCT : 0),
        size());
  }