- E object
object is in the queue.
Returns true if the element is found.
Uses the Object.== of elements in the queue to check
for whether they are equal to
Equal objects objects must have the same priority
according to the comparison function.
That is, if
a == b then
comparison(a, b) == 0.
If that is not the case, this check might fail to find
@override bool contains(E object) => _locate(object) >= 0;