Method cardinality

Bcore/src/main/cpp/Dobby/tests/catch.hpp:5811–5813

  }
  virtual auto parse(std::string const &exeName, TokenStream const &tokens) const -> InternalParseResult = 0;
  virtual auto cardinality() const -> size_t {
    return 1;
  }

  auto parse(Args const &args) const -> InternalParseResult {
    return parse(args.exeName(), TokenStream(args));