<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def concat(*cols):
 """ Concatenates multiple input columns together into a single column. The function works with strings, binary and compatible array columns. [Row(s=u'abcd123')] [Row(arr=[1, 2, 3, 4, 5]), Row(arr=None)] """

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