retainWhere method
void retainWhere(Removes all elements not matched by test from the queue.
The test function must not throw or modify the queue.
Source
void retainWhere(bool test(E element)) {
  _filter(test, false);
}
    © 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/DoubleLinkedQueue/retainWhere.html