public Type getDataType(int index) {
    return argumentTypes.get(index);
  }
Get the data type of the input child expression at the specified index.

@param index column index
@return the data type of the input child expression at the specified index
iotdb-api/udf-api/src/main/java/org/apache/iotdb/udf/api/customizer/parameter/FunctionArguments.java