code: def shiftLeft(col, numBits):
      
      sc = SparkContext._active_spark_context
      return Column(sc._jvm.functions.shiftLeft(_to_java_column(col), numBits))
docs: Shift the given value numBits left.
  
      >>> spark.createDataFrame([(21,)], ['a']).select(shiftLeft('a', 1).alias('r')).collect()
      [Row(r=42)]