K, V>.unmodifiable constructor
Creates an unmodifiable hash based map containing the entries of
The keys must all be instances of
K and the values of
other map itself can have any type.
The map requires the keys to implement compatible
hashCode, and it allows
null as a key.
The created map iterates keys in a fixed order,
preserving the order provided by
The resulting map behaves like the result of Map.from, except that the map returned by this constructor is not modifiable.
external factory Map.unmodifiable(Map other);