@Override
  public void validate(UDFParameterValidator validator) throws Exception {
    validator
        .validateInputSeriesDataType(0, Type.DOUBLE, Type.FLOAT, Type.INT32, Type.INT64)
        .validate(
            x ->
                ((String) x).equalsIgnoreCase("Haar")
                    || ((String) x).equalsIgnoreCase("DB2")
                    || ((String) x).equalsIgnoreCase("DB4")
                    || ((String) x).equalsIgnoreCase("DB6")
                    || ((String) x).equalsIgnoreCase("DB8")
                    || ((String) x).equalsIgnoreCase(""),
            "Method not supported, please input coefficient and leave method blank.",
            validator.getParameters().getStringOrDefault("method", ""))
        .validate(
            x -> (int) x > 0,
            "layer has to be a positive integer.",
            validator.getParameters().getIntOrDefault("layer", 1));
  }
This function calculates inverse discrete wavelet transform of an input series, which is composed
of multiple layers. Input series must be an integer exponent of 2. Input series is treated as
sampled in equal distances.
library-udf/src/main/java/org/apache/iotdb/library/frequency/UDTFIDWT.java