setToString method
String setToString(Convert a Set to a string as {each, element, as, string}.
Handles circular references where converting one of the elements to a string ends up converting set to a string again.
Source
static String setToString(Set set) =>
    IterableBase.iterableToFullString(set, '{', '}');
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dartlang.org/stable/1.24.3/dart-collection/SetBase/setToString.html