def addChromosomeInstance(
            self, chr_num, reference_id, reference_label, chr_type=None):
        """
        Add the supplied chromosome as an instance within the given reference
        :param chr_num:
        :param reference_id: for example, a build id like UCSC:hg19
        :param reference_label:
        :param chr_type: this is the class that this is an instance of.
        typically a genome-specific chr

        :return:

        """
        family = Family(self.graph)
        chr_id = makeChromID(str(chr_num), reference_id, 'MONARCH')
        chr_label = makeChromLabel(str(chr_num), reference_label)

        self.model.addIndividualToGraph(chr_id, chr_label, self.globaltt['chromosome'])
        if chr_type is not None:
            self.model.addType(chr_id, chr_type)

        # add the build-specific chromosome
        # as a member of the build  (both ways)
        family.addMember(reference_id, chr_id)
        family.addMemberOf(chr_id, reference_id)   # usage dependent, todo: ommit

        return
Add the supplied chromosome as an instance within the given reference
        :param chr_num:
        :param reference_id: for example, a build id like UCSC:hg19
        :param reference_label:
        :param chr_type: this is the class that this is an instance of.
        typically a genome-specific chr

        :return: