@Override
  public TSDataType[] getDataTypes() {
    return new TSDataType[] {layerReaderDataType};
  }
this is a special transformer which outputs data just as input without any modification.

<p>i.e. it's just the function f(x) = x.

<p>It's mainly used for a UDF with aggregation query as its parameters.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/transformation/dag/transformer/unary/TransparentTransformer.java