shrinkAndFree

        pub fn shrinkAndFree(self: *Self, allocator: Allocator, new_capacity: usize) void {
            assert(new_capacity <= self.cap);

            // Cannot shrink to smaller than the current queue size without invalidating the heap property
            assert(new_capacity >= self.items.len);

            const old_memory = self.allocatedSlice();
            const new_memory = allocator.realloc(old_memory, new_capacity) catch |e| switch (e) {
                error.OutOfMemory => { // no problem, capacity is still correct then.
                    return;
                },
            };

            self.items.ptr = new_memory.ptr;
            self.cap = new_memory.len;
        }