def already_backported(branch, since_tag=None):
    """return set of PRs that have been backported already"""
    if since_tag is None:
        since_tag = check_output(['git','describe', branch, '--abbrev=0']).decode('utf8').strip()
    cmd = ['git', 'log', (since_tag, branch) % '%s..%s', '--oneline']
    lines = check_output(cmd).decode('utf8')
    return set(int(num) for num in backport_re.findall(lines))
dataset/ETHPy150Open statsmodels/statsmodels/tools/backport_pr.py/already_backported/swapped operands of `%`