default boolean isNullable() {
        return getAsBoolean(HasNullableUtil.NULLABLE).orElse(true);
    }
Returns whether or not this column can hold {@code null} values.

@return  {@code true} if null values are tolerated, else {@code false}
runtime-parent/runtime-config/src/main/java/com/speedment/runtime/config/trait/HasNullable.java