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 representation.
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
@override
String toString() {
  String hexBuilder = "";
  for (int byte in _bytes) {
    hexBuilder += byte.toRadixString(16).padLeft(2, '0');
  }
  return '${hexBuilder.substring(0, 8)}-${hexBuilder.substring(8, 12)}-${hexBuilder.substring(12, 16)}-${hexBuilder.substring(16, 20)}-${hexBuilder.substring(20, 32)}';
}