Method of

core/src/test/java/org/apache/calcite/test/RelBuilderTest.java:6002–6002

(String name,
        Function<RelDataTypeFactory, RelDataType> protoType,
        SqlTypeFamily family, boolean optional)

    }

    static Arg of(String name,
        Function<RelDataTypeFactory, RelDataType> protoType,
        SqlTypeFamily family, boolean optional) {
      return new Arg() {