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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 refresh_client(self, from_dt=None, to_dt=None):
 """ Refreshes the ContactsService endpoint, ensuring that the contacts data is up-to-date. """

        params_contacts = dict(self.params)
        params_contacts.update({
            'clientVersion': '2.1',
            'locale': 'en_US',
            'order': 'last,first',
        })
        req = self.session.get(
            self._contacts_refresh_url,
            params=params_contacts
        )
        self.response = req.json()
        params_refresh = dict(self.params)
        params_refresh.update({
            'prefToken': req.json()["prefToken"],
            'syncToken': req.json()["syncToken"],
        })
        self.session.post(self._contacts_changeset_url, params=params_refresh)
        req = self.session.get(
            self._contacts_refresh_url,
            params=params_contacts
        )
        self.response = req.json()