presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/WriteMapping.java/WriteMapping/WriteMapping
class WriteMapping:    private WriteMapping(String dataType, WriteFunction writeFunction, WriteNullFunction writeNullFunction)
    {
        this.dataType = requireNonNull(dataType, "dataType is null");
        this.writeFunction = requireNonNull(writeFunction, "writeFunction is null");
        this.writeNullFunction = requireNonNull(writeNullFunction, "writeNullFunction is null");
    }