HashMap<K, V>.fromEntries constructor
Creates a HashMap containing the entries of entries.
Returns a new HashMap<K, V> where all entries of entries
have been added in iteration order.
If multiple entries have the same key,
later occurrences overwrite the earlier ones.
Implementation
factory HashMap.fromEntries(Iterable<MapEntry<K, V>> entries) =>
HashMap<K, V>()..addEntries(entries);