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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 groupByNode(requestContext, seriesList, nodeNum, callback):
 """ Takes a serieslist and maps a callback to subgroups within as defined by a common node. Example:: &target=groupByNode(ganglia.by-function.*.*.cpu.load5,2,"sumSeries") Would return multiple series which are each the result of applying the "sumSeries" function to groups joined on the second node (0 indexed) resulting in a list of targets like:: sumSeries(ganglia.by-function.server1.*.cpu.load5), """

    return groupByNodes(requestContext, seriesList, callback, nodeNum)