code: private static <K, V> boolean colorOf(final OMVRBTreeEntry<K, V> p) {
      return (p == null ? BLACK : p.getColor());
    }
docs: Balancing operations.
  
  Implementations of rebalancings during insertion and deletion are slightly different than the CLR version. Rather than using
  dummy nilnodes, we use a set of accessors that deal properly with null. They are used to avoid messiness surrounding nullness
  checks in the main algorithms.