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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 conv(col, fromBase, toBase):
 """ Convert a number in a string column from one base to another. [Row(hex=u'15')] """

    sc = SparkContext._active_spark_context
    return Column(sc._jvm.functions.conv(_to_java_column(col), fromBase, toBase))