// collect drop list
        for (MetadataGraphVertex v : g.getVertices()) {
            if (!visited.contains(v)) {
                dropList.add(v);
            }
        }

        if (dropList.size() < 1) {
            return g;
        }

        // now - drop vertices
        TreeSet<MetadataGraphVertex> vertices = g.getVertices();

  }

  private void addToCache(K key, V value) {
    addToCache(new CacheEntry<K, V>(key, value));
  }

  private void addToCache(CacheEntry<K, V> entry) {
    // Slide new entry into first cache position. Drop previous entry in second cache position.
    cacheEntry2 = cacheEntry1;
    cacheEntry1 = entry;
  }

  private static final class CacheEntry<K, V> {
    final K key;
    final V value;

  }

  static double select(int k, double[] array) {
    // This is basically a copy of com.google.math.Rank#select, with a small change in the method
    // signature: we make k 0-based rather than 1-based; and we drop from and to, and always work on
    // the whole array.
    int from = 0;
    int to = array.length - 1;

    while (true) {
      if (to <= from + 1) {
        // Two or less elements left.

  }

  static double select(int k, double[] array) {
    // This is basically a copy of com.google.math.Rank#select, with a small change in the method
    // signature: we make k 0-based rather than 1-based; and we drop from and to, and always work on
    // the whole array.
    int from = 0;
    int to = array.length - 1;

    while (true) {
      if (to <= from + 1) {
        // Two or less elements left.

@ElementTypesAreNonnullByDefault
class CompactLinkedHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends CompactHashMap<K, V> {
  // TODO(lowasser): implement removeEldestEntry so this can be used as a drop-in replacement

  /** Creates an empty {@code CompactLinkedHashMap} instance. */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      CompactLinkedHashMap<K, V> create() {

    // in the opposite order from how they were added so we need to reverse the list to fulfill our
    // contract.
    // This is somewhat annoying, but turns out to be very fast in practice. Alternatively, we could
    // drop the contract on the method that enforces this queue like behavior since depending on it
    // is likely to be a bug anyway.

    // N.B. All writes to the list and the next pointers must have happened before the above

            try {
                VersionRange parentRange = versionParser.parseVersionRange(parent.getVersion());
                if (!parentRange.contains(versionParser.parseVersion(version))) {
                    // version skew drop back to resolution from the repository
                    return null;
                }

                // Validate versions aren't inherited when using parent ranges the same way as when read externally.

@ElementTypesAreNonnullByDefault
class CompactLinkedHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends CompactHashMap<K, V> {
  // TODO(lowasser): implement removeEldestEntry so this can be used as a drop-in replacement

  /** Creates an empty {@code CompactLinkedHashMap} instance. */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      CompactLinkedHashMap<K, V> create() {

@ElementTypesAreNonnullByDefault
class CompactHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMap<K, V> implements Serializable {
  /*
   * TODO: Make this a drop-in replacement for j.u. versions, actually drop them in, and test the
   * world. Figure out what sort of space-time tradeoff we're actually going to get here with the

            thread.setDaemon( true );
            thread.start();
        }
    }
    void tryClose() {
        synchronized( LOCK ) {

            /* Yes, there is the potential to drop packets
             * because we might close the socket during a
             * request. However the chances are slim and the
             * retry code should ensure the overall request