code: function(reverse) {
          var focusModel = this.focusModel;
          var address = reverse ? focusModel.prevAddress() : focusModel.nextAddress();
  
          focusModel.focusIn(address.rowKey, address.columnName, true);
      }
docs: Moves focus to the next cell, and starts editing the cell.
  @param {Boolean} reverse - if set to true, find the previous cell instead of next cell