Returns the active SparkSession for the current thread, returned by the builder.
        >>> s = SparkSession.getActiveSession()
        >>> l = [('Alice', 1)]
        >>> rdd = s.sparkContext.parallelize(l)
        >>> df = s.createDataFrame(rdd, ['name', 'age'])
        >>> df.select("age").collect()
        [Row(age=1)]

def getActiveSession(cls):
        """
        Returns the active SparkSession for the current thread, returned by the builder.
        >>> s = SparkSession.getActiveSession()
        >>> l = [('Alice', 1)]
        >>> rdd = s.sparkContext.parallelize(l)
        >>> df = s.createDataFrame(rdd, ['name', 'age'])
        >>> df.select("age").collect()
        [Row(age=1)]
        """
        from pyspark import SparkContext
        sc = SparkContext._active_spark_context
        if sc is None:
            return None
        else:
            if sc._jvm.SparkSession.getActiveSession().isDefined():
                SparkSession(sc, sc._jvm.SparkSession.getActiveSession().get())
                return SparkSession._activeSession
            else:
                return None