Return the Cartesian product of this RDD and another one, that is, the
RDD of all pairs of elements (a, b) where a is in self and
b is in other.
New in version 0.7.0.
the Cartesian product of this RDD and another one
>>> rdd = sc.parallelize([1, 2])
[(1, 1), (1, 2), (2, 1), (2, 2)]