import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@link GraphConnections} for directed graphs.
 *
 * @author James Sexton
 * @author Jens Nyman
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
final class DirectedGraphConnections<N, V> implements GraphConnections<N, V> {
  /**
   * A wrapper class to indicate a node is both a predecessor and successor while still providing