code: public static <T> BinaryValue getKey(T domainObject, BinaryValue defaultKey)
      {
          BinaryValue key = getKey(domainObject);
          if (key == null)
          {
              key = defaultKey;
          }
          return key;
      }
docs: Attempts to get a key from <code>domainObject</code> by looking for a
  {@literal @RiakKey} annotated member. If non-present it simply returns
  <code>defaultKey</code>
  
  @param <T> the type of <code>domainObject</code>
  @param domainObject the object to search for a key
  @param defaultKey the pass through value that will get returned if no key
  found on <code>domainObject</code>
  @return either the value found on <code>domainObject</code>;s
  {@literal @RiakKey} member or <code>defaultkey</code>