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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_ordering_field_lookup(self, field_name):
 """ get real model field to order by """

        field = field_name
        get_field = getattr(self, "get_%s_ordering_field" % field_name, None)
        if get_field:
            field = get_field()
        return field