docs: function validateVars() {
    _.each(xml2js.CLASSES, function(classSpec, className) {
      var valid = _.pick(classSpec.variables, function(varSpec, varName) {
        return ofValidType(varSpec, className + '.' + varName, className);
      });
      if (xml2js.opts.strict) {
        xml2js.CLASSES[className].variables = valid;
      }
    });
  }