Enhance docstring for pairwise iteration

Added docstring explaining the use of itertools.tee for independent iterators.

Author: cclauss

data_structures/arrays/pairwise_iteration.py

@@ -58,6 +58,7 @@ def pairwise_iteration_tee(iterable: Iterable) -> Iterator[tuple]:
         ...     ['ATG','GCT','TGC','TAA'],
         ...     [],
         ... ))
+        True
     """
     # Uses itertools.tee to create two independent iterators (a and b)
     # from the iterable. This means we can use next() on each one