public boolean typeEquals(TypeEnum typeEnum) {
    return returnType == null || returnType.getTypeEnum().equals(typeEnum);
  }
Return whether the type of this ColumnTransformer is equal to certain type. If this
ColumnTransformer is {@link NullColumnTransformer}, return {@code true}.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/transformation/dag/column/ColumnTransformer.java