code: def union(self, *dstreams):
          
          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)
docs: Create a unified DStream from multiple DStreams of the same
          type and same slide duration.