code: function getDisplayValue (item) {
      return $q.when(getItemText(item) || item).then(function(itemText) {
        if (itemText && !angular.isString(itemText)) {
          $log.warn('md-autocomplete: Could not resolve display value to a string. ' +
            'Please check the `md-item-text` attribute.');
        }
  
        return itemText;
      });
  
      /**
       * Getter function to invoke user-defined expression (in the directive)
       * to convert your object to a single string.
       */
      function getItemText (item) {
        return (item && $scope.itemText) ? $scope.itemText(getItemAsNameVal(item)) : null;
      }
    }
docs: Returns the display value for an item.
  @param item
  @returns {*}