code: function _closeAll(paneId) {
          _forEachPaneOrPanes(paneId, function (pane) {
              var closedList = pane.getViewList();
              closedList.forEach(function (file) {
                  _removeFileFromMRU(pane.id, file);
              });
  
              pane._reset();
              exports.trigger("workingSetRemoveList", closedList, pane.id);
          });
      }
docs: Closes all files in the specified pane or panes
  @param {!string} paneId - id of the pane in which to open the document
  This function does not fail if the file is not open