IndexedSet is a Set implementation that computes an index for each of its elements and exposes this mapping through the  operator.
Use this package as a library
1. Depend on it
Add this to your package's pubspec.yaml file:
dependencies: indexed_set: ^1.0.0+2
2. Install it
You can install packages from the command line:
$ pub get
Alternatively, your editor might support
Check the docs for your editor to learn more.
3. Import it
Now in your Dart code, you can use: