private DeviceViewNode initDeviceViewNode(TypeProvider typeProvider, int childNum)
      throws IllegalPathException {
    DeviceViewNode deviceViewNode =
        new DeviceViewNode(new PlanNodeId("DeviceViewNode"), null, null, null);
    for (int i = 0; i < childNum; i++) {
      AlignedSeriesScanNode alignedSeriesScanNode =
          new AlignedSeriesScanNode(
              new PlanNodeId(String.format("AlignedSeriesScanNode%d", i)),
              new AlignedPath(String.format("root.sg.d%d", i), "s1"));
      deviceViewNode.addChild(alignedSeriesScanNode);
    }
    return deviceViewNode;
  }
This method will init a DeviceViewNode with @childNum alignedSeriesScanNode as children.

@param childNum the number of children
@return a DeviceViewNode with @childNum alignedSeriesScanNode as children
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/plan/planner/PipelineBuilderTest.java