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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 get_robotstxt_parser(url, session=None):
 """Get a RobotFileParser for the given robots.txt URL."""

    rp = robotparser.RobotFileParser()
    try:
        req = urlopen(url, session, max_content_bytes=MaxContentBytes, raise_for_status=False)
    except Exception:
        # connect or timeout errors are treated as an absent robots.txt
        rp.allow_all = True
    else:
        if req.status_code >= 400:
            rp.allow_all = True
        elif req.status_code == 200:
            rp.parse(req.text.splitlines())
    return rp