CanonicalizedMap<C, K, V> constructor
*<Null safety>*
CanonicalizedMap<C, K, V>(C canonicalize(K key), {bool isValidKey(K key)})
Implementation
CanonicalizedMap(C Function(K key) canonicalize,
{bool Function(K key)? isValidKey})
: _canonicalize = canonicalize,
_isValidKeyFn = isValidKey;