toString method
override
 A string representation of this object.
Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string represetion.
Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.
Implementation
String toString() => "MapEntry(${key.toString()}: ${value.toString()})";
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dart.dev/stable/2.13.0/dart-core/MapEntry/toString.html