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