code: function validateForm(form, cb) {
  
    async.series([function(callback) {
      fs.exists(form, function(exists) {
        if (exists) {
          callback(null);
        } else {
          callback('File ' + path.basename(form) + ' referenced by metadata.json does not exists');
        }
      });
    },
      function(callback) {
        validateJSonStructure(form, callback);
      }
    ], function(err, data) {
      cb(err, data);
    });
  }
docs: Validate the received form file.
  
  @param {string} form path to the form file to be validated
  @param {function} cb callback