code: public void existenceCheck(final Nodes nodes, final String nodeNameForDebugging) throws XMLParsingException {
          if (nodes.size() == 0) {
              throw new XMLParsingException("Message doesn't contain a " + nodeNameForDebugging + "node!");
          }
      }
docs: Does nothing if nodes contains at least one node. Throws InvalidCfgDocException otherwise.
  
  @param nodes
  @param nodeNameForDebugging
  @throws XMLParsingException