// checkIfSeriesNeedToBeFixed scans all value fields of all provided frames and determines whether the resulting mathexp.Series
// needs to be updated so each series could be identifiable by labels.
// NOTE: applicable only to only datasources.DS_GRAPHITE and datasources.DS_TESTDATA data sources
// NOTE: applicable only to some datas ources (datasources.DS_GRAPHITE, datasources.DS_TESTDATA, etc.); a more general solution should be investigated
// returns a function that patches the mathexp.Series with information from data.Field from which it was created if the all series need to be fixed. Otherwise, returns nil