def pair_table_to_dot_bracket(pt, strand_break='+'):
    """
    Inverse of the make_pair_table function.
    """
    assert len(strand_break) == 1
    out = []
    for si, strand in enumerate(pt):
        if out:
            out.append(strand_break)
        for di, pair in enumerate(strand):
            if pair is None:
                out.append('.')
            else:
                locus = si, di
                if locus < pair:
                    out.append('(')
                else:
                    out.append(')')
    return out
