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