remove duplicates

[Adrian Mocanu]

I have a DStream like this:
..RDD[a,b],RDD[b,c]..

Is there a way to remove duplicates across the entire DStream? Ie: I would like 
the output to be (by removing one of the b's):
..RDD[a],RDD[b,c]..  or ..RDD[a,b],RDD[c]..

Thanks
-Adrian