code: function endOperation(cm) {
      var op = cm.curOp, group = op.ownsGroup;
      if (!group) return;
  
      try { fireCallbacksForOps(group); }
      finally {
        operationGroup = null;
        for (var i = 0; i < group.ops.length; i++)
          group.ops[i].cm.curOp = null;
        endOperations(group);
      }
    }
docs: Finish an operation, updating the display and signalling delayed events