code: function(elem, prop) {
          var $elem = $(elem);
  
          if (!prop) {
              prop = 'margin-left';
          }
  
          var startingPoint = parseInt($elem.css(prop));
          if (isNaN(startingPoint)) {
              startingPoint = 0;
          }
  
          for (var i = 0; i <= Garnish.SHAKE_STEPS; i++) {
              (function(i) {
                  setTimeout(function() {
                      Garnish.shake._properties = {};
                      Garnish.shake._properties[prop] = startingPoint + (i % 2 ? -1 : 1) * (10 - i);
                      $elem.velocity(Garnish.shake._properties, Garnish.SHAKE_STEP_DURATION);
                  }, (Garnish.SHAKE_STEP_DURATION * i));
              })(i);
          }
      }
docs: Shakes an element.
  
  @param {object}  elem Either an actual element or a jQuery collection.
  @param {string} prop The property that should be adjusted (default is 'margin-left').