Switching between batches from two different bucket iterator objects

I have two below BucketIterator objects:
Iterator1 and Iterator2

For training I have to use two Iterators (Mixing is not possible in my case)
Now while training I am using the batches from these two iterators
say batch1 from Iterator1 and batch2 from Iterator2

I want to use these batches(batch1 and batch2) alternatively while training … But I am not able to do that … because what I learned till now about bucket iterator is … there is no next() and it can only iterates through for(itr in iterator1)

That is why currently I am using in pipeline basis … first completing training with iterator1 and then iterator2

can you please let me know how I can use these interchangeably?
Thank you…