@Override
  public List<PartialPath> visitTimeSeriesOperand(
      TimeSeriesViewOperand timeSeriesOperand, Void context) {
    String pathString = timeSeriesOperand.getPathString();
    try {
      PartialPath path = new PartialPath(pathString);
      return Collections.singletonList(path);
    } catch (IllegalPathException e) {
      // the path is illegal!
      throw new RuntimeException(e);
    }
  }
Use this visitor to find all the paths of time series used in one expression.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/view/visitor/GetSourcePathsVisitor.java