Python queue keep only the latest element with specific condition

Let's say in the traditional producer/consumer pattern, the producer will produce two types of elements, A& B. The buffer queue should implement the following logics:

• Thread safe.
• FIFO
• All A can safely stay in the queue, which denote important task.
• Whenever a new B arrive, kick out all preceeding B in the queue and append to the end of the queue, which denote the latest non-important task.
• The order of elements should be preserved.
• The consumer pop element just like normal.

For simplicity, just imagine the size of the queue is unlimited.
Is it possible to implement this without using 2 queues?