<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def read_xml(filename):
 """ Use et to read in a xml file, or string, into a Element object. :param filename: File to parse. :return: lxml._elementTree object or None """

    parser = et.XMLParser(remove_blank_text=True)
    isfile=False
    try:
        isfile = os.path.exists(filename)
    except ValueError as e:
        if 'path too long for Windows' in str(e):
            pass
        else:
            raise
    try:
        if isfile:
            return et.parse(filename, parser)
        else:
            r = et.fromstring(filename, parser)
            return r.getroottree()
    except IOError:
        log.exception('unable to open file [[}]'.format(filename))
    except et.XMLSyntaxError:
        log.exception('unable to parse XML [{}]'.format(filename))
        return None
    return None