Function is

src/toml.hpp:3587–3612

		template <typename T>
		TOML_PURE_INLINE_GETTER
		bool is() const noexcept
		{
			using type = impl::remove_cvref<impl::unwrap_node<T>>;
			static_assert(toml::is_value<type> || toml::is_container<type>,
						  "The template type argument of node::is() must be one of:" TOML_SA_UNWRAPPED_NODE_TYPE_LIST);

			if constexpr (std::is_same_v<type, table>)
				return is_table();
			else if constexpr (std::is_same_v<type, array>)
				return is_array();
			else if constexpr (std::is_same_v<type, std::string>)
				return is_string();
			else if constexpr (std::is_same_v<type, int64_t>)
				return is_integer();
			else if constexpr (std::is_same_v<type, double>)
				return is_floating_point();
			else if constexpr (std::is_same_v<type, bool>)
				return is_boolean();
			else if constexpr (std::is_same_v<type, date>)
				return is_date();
			else if constexpr (std::is_same_v<type, time>)
				return is_time();
			else if constexpr (std::is_same_v<type, date_time>)
				return is_date_time();
		}

		TOML_PURE_GETTER
		virtual table* as_table() noexcept = 0;