def METHOD_NAME(self, objid):
    subdetid = self.get_subdetid(objid)
    discriminator = self.get_discriminator(objid)
    ndiscriminator = {key: [] for key in discriminator}
    # open TrackerTree.root file
    treeFile = ROOT.TFile(os.path.join(self.config.jobDataPath,
                                       ".TrackerTree.root"))
    tree = treeFile.Get("TrackerTreeGenerator/TrackerTree/TrackerTree")
    for entry in tree:
        # check if entry is part of the structure
        if (entry.SubdetId == subdetid):
            for structure in discriminator:
                ndiscriminator[structure].append(getattr(entry, structure))
    for structure in discriminator:
        ndiscriminator[structure] = [x for x in ndiscriminator[structure] if x != 0]
    return [len(set(ndiscriminator[structure]))
            for structure in discriminator]