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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def concat_ws(sep, *cols):
 """ Concatenates multiple input string columns together into a single string column, using the given separator. [Row(s=u'abcd-123')] """

    sc = SparkContext._active_spark_context
    return Column(sc._jvm.functions.concat_ws(sep, _to_seq(sc, cols, _to_java_column)))