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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(self, instance, acl):
 """Get an ACL by ID belonging to the instance specified by name. :param str instance: The name of the instance from which to fetch the ACL. :param str acl: The ID of the ACL to fetch. :returns: An :py:class:`Acl` object, or None if ACL does not exist. :rtype: :py:class:`Acl` """

        base_url = self._url.format(instance=instance)
        url = '{base}{aclid}/'.format(base=base_url, aclid=acl)
        response = requests.get(url, **self._default_request_kwargs)
        data = self._get_response_data(response)
        return self._concrete_acl(data)