default ToBigDecimalNullable<ENTITY> asBigDecimal() {
        return mapToBigDecimalIfPresent(val -> {
            if (val instanceof BigDecimal) {
                return (BigDecimal) val;
            } else throw new SpeedmentFieldException(format(
                "Expected field %s to be of type BigDecimal, but it was not.",
                identifier()
            ));
        });
    }
Returns an {@link ToBigDecimalNullable} expression that has the value of
this field but casted to a {@link BigDecimal}.

@return  expression for this value after mapper has been applied

@since 3.1.0
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/ReferenceField.java