Method required

CvPlot/ext/catch2/inc/catch.hpp:9195–9198

        };

        auto required() -> DerivedT & {
            m_optionality = Optionality::Required;
            return static_cast<DerivedT &>( *this );
        };

        auto isOptional() const -> bool {
            return m_optionality == Optionality::Optional;