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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 system_summary(providername=None):
 """ returns SystemSummary class from mentioned provider """

    _providername = providername
    if not _providername:
        _providername = provider_check()

    import_str = 'netshowlib.%s.system_summary' % _providername
    return import_module(import_str).SystemSummary()