code: @Override
      public boolean contains(final KEY key) {
          try {
              verifyID(key);
          } catch (VerificationFailedException ex) {
              new FatalImplementationErrorException("Contains check failed because of an invalid key!", this, ex);
              return false;
          }
          return entryMap.containsKey(key);
      }
docs: {@inheritDoc}
  
  @param key {@inheritDoc}
  
  @return {@inheritDoc}