*       type.
 * </dl>
 *
 * <h2>Ranges</h2>
 *
 * <ul>
 *   <li>{@link Range}
 *   <li>{@link RangeMap}
 *   <li>{@link RangeSet}
 *   <li>{@link DiscreteDomain}
 *   <li>{@link ContiguousSet}
 * </ul>
 *
 * <h2>Classes of static utility methods</h2>
 *
 * <ul>
 *   <li>{@link Collections2}
 *   <li>{@link Comparators}
 *   <li>{@link Iterables}

 *       type.
 * </dl>
 *
 * <h2>Ranges</h2>
 *
 * <ul>
 *   <li>{@link Range}
 *   <li>{@link RangeMap}
 *   <li>{@link RangeSet}
 *   <li>{@link DiscreteDomain}
 *   <li>{@link ContiguousSet}
 * </ul>
 *
 * <h2>Classes of static utility methods</h2>
 *
 * <ul>
 *   <li>{@link Collections2}
 *   <li>{@link Comparators}
 *   <li>{@link Iterables}

   *
   * <ul>
   *   <li>{@code view.equals(view)} evaluates to {@code true} (but any other {@code equals()}
   *       expression involving {@code view} will throw)
   *   <li>{@code hashCode()} does not throw
   *   <li>if {@code node} is re-added to the network after having been removed, {@code view}'s
   *       behavior is undefined
   * </ul>
   *

 *
 * <p>The DataIndexHelper supports:</p>
 * <ul>
 *   <li>Concurrent crawling of multiple data configurations</li>
 *   <li>Thread pool management for crawler execution</li>
 *   <li>Session-based crawling with cleanup operations</li>
 *   <li>Old document deletion after successful crawling</li>
 *   <li>Crawling execution monitoring and timing</li>
 * </ul>
 */
public class DataIndexHelper {

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.

 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.