code: public ParsedNode getChild(String namespace, String name) throws ParsedNodeException {
          ParsedNode returnNode = null;
          for (ParsedNode node : children) {
              if (nodeMatches(node, namespace, name)) {
                  if (returnNode != null) {
                      throw new ParsedNodeException("Multiple nodes match "+namespace+"/"+name);
                  }
                  returnNode = node;
              }
          }
          return returnNode;
      }
docs: Returns the ParsedNode defined by the given namespace and name.
  @throws liquibase.parser.core.ParsedNodeException if multiple nodes match.