builds the list of BAM tags to be added to output BAMs

def build_bam_tags():
    '''builds the list of BAM tags to be added to output BAMs'''
    #pylint: disable=unused-argument
    def _combine_filters(fam, paired_align, align):
        filters = [x.filter_value for x in [fam, align] if x and x.filter_value]
        if filters:
            return ";".join(filters).replace('; ', ';')
        return None

    boolean_tag_value = {True:1}
    tags = [
        BamTag("X0", "Z",
               ("filter (why the alignment was excluded)"),
               _combine_filters),
        BamTag("X1", "Z",
               ("leftmost~rightmost matched pair positions"),
               lambda fam, pair, align: pair.positions('{left}~{right}')),
        BamTag("X2", "Z",
               ("L~R CIGARs"),
               lambda fam, pair, align: pair.cigars('{left}~{right}')),
        BamTag("X3", "i",
               "unique identifier for this alignment family",
               lambda fam, pair, align: fam.umi_sequence),
        BamTag("X4", "Z",
               ("L~R UMT barcodes for this alignment family; because "
                "of fuzzy matching the family UMT may be distinct "
                "from the UMT of the original alignment"),
               lambda fam, pair, align: fam.umt('{left}~{right}')),
        BamTag("X5", "i",
               "family size (number of align pairs in this family)",
               lambda fam, pair, align: fam.included_pair_count),
        BamTag("X6", "i",
               ("presence of this tag signals that this alignment "
                "would be the template for the consensus alignment"),
               lambda fam, pair, align: boolean_tag_value.get(fam.is_consensus_template(align), None))]
    return tags