Create a unified DStream from multiple DStreams of the same
        type and same slide duration.

def union(self, *dstreams):
        """
        Create a unified DStream from multiple DStreams of the same
        type and same slide duration.
        """
        if not dstreams:
            raise ValueError("should have at least one DStream to union")
        if len(dstreams) == 1:
            return dstreams[0]
        if len(set(s._jrdd_deserializer for s in dstreams)) > 1:
            raise ValueError("All DStreams should have same serializer")
        if len(set(s._slideDuration for s in dstreams)) > 1:
            raise ValueError("All DStreams should have same slide duration")
        cls = SparkContext._jvm.org.apache.spark.streaming.api.java.JavaDStream
        jdstreams = SparkContext._gateway.new_array(cls, len(dstreams))
        for i in range(0, len(dstreams)):
            jdstreams[i] = dstreams[i]._jdstream
        return DStream(self._jssc.union(jdstreams), self, dstreams[0]._jrdd_deserializer)