raigons/bureauinteligencia — comment on commit 3be964034e241bf46390a896cb8e1f461e930f4e
File: core/Charts/XmlCharts/MultiSerie/XmlMultiSeriesCombinationColumnLine.php line 31
By raigons:

this function has been added because when the "datacenter ChartBuilder" class was trying to set a dataset as a line to a specific Y axis, there was a param duplicated inside xml file (parentYAxis). So this verifying has been wrote to avoid this problem, allowing adding the attribute only if it does not exists.