nlohmann::ordered_map::operator[]

T&
operator[](key_type const& key);

T const&
operator[](key_type const& key) const;

template<class KeyType>
requires detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value
T const&
operator[](KeyType&& key) const;

template<class KeyType>
requires detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value
T&
operator[](KeyType&& key);