code: function (node, validation) {
  
              var self = this;
  
              validation = self._splitValidation(validation);
  
              if (!validation) {
                  return false;
              }
  
              return node.each(function () {
  
                  var $this = $(this),
                      validationData = $this.attr(_data.validation),
                      validationArray = (validationData && validationData.length) ? self._splitValidation(validationData) : [],
                      oneValidation;
  
                  for (var i = 0; i < validation.length; i++) {
  
                      oneValidation = self._formatValidation(validation[i]);
  
                      if ($.inArray(oneValidation, validationArray) === -1) {
                          validationArray.push(oneValidation);
                      }
                  }
  
                  if (validationArray.length) {
                      $this.attr(_data.validation, self._joinValidation(validationArray));
                  }
  
              });
  
          }
docs: API method to handle the addition of "data-validation" arguments.
  Note: ONLY the predefined validation arguments are allowed to be added
  inside the "data-validation" attribute (see configuration).
  
  @param {Object} node jQuery objects
  @param {String|Array} validation arguments to add in the node(s) "data-validation"
  
  @returns {*}