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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def issues_closed_since(period=timedelta(days=365), project="arokem/python-matlab-bridge", pulls=False):
 """Get all issues closed since a particular point in time. period can either be a datetime object, or a timedelta object. In the latter case, it is used as a time before the present. """


    which = 'pulls' if pulls else 'issues'

    if isinstance(period, timedelta):
        since = round_hour(datetime.utcnow() - period)
    else:
        since = period
    url = "https://api.github.com/repos/%s/%s?state=closed&sort=updated&since=%s&per_page=%i" % (project, which, since.strftime(ISO8601), PER_PAGE)
    allclosed = get_paged_request(url, headers=make_auth_header())
    
    filtered = [ i for i in allclosed if _parse_datetime(i['closed_at']) > since ]
    if pulls:
        filtered = [ i for i in filtered if _parse_datetime(i['merged_at']) > since ]
        # filter out PRs not against master (backports)
        filtered = [ i for i in filtered if i['base']['ref'] == 'master' ]
    else:
        filtered = [ i for i in filtered if not is_pull_request(i) ]
    
    return filtered