@Override
  public void validate(UDFParameterValidator validator) throws Exception {
    validator
        .validateInputSeriesNumber(1)
        .validateInputSeriesDataType(0, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE);
  }
This function calculates skew of input series.
library-udf/src/main/java/org/apache/iotdb/library/dprofile/UDAFSkew.java