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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_request_token(self):
 """ Obtain a temporary request token to authorize an access token and to sign the request to obtain the access token """

        if self.request_token is None:
            get_params = {}
            if self.parameters:
                get_params.update(self.parameters)
            get_params['oauth_callback'] \
                = self.request.build_absolute_uri(self.callback_url)
            rt_url = self.request_token_url + '?' + urlencode(get_params)
            oauth = OAuth1(self.consumer_key,
                           client_secret=self.consumer_secret)
            response = requests.post(url=rt_url, auth=oauth)
            if response.status_code not in [200, 201]:
                raise OAuthError(
                    _('Invalid response while obtaining request token'
                      ' from "%s".') % get_token_prefix(
                          self.request_token_url))
            self.request_token = dict(parse_qsl(response.text))
            self.request.session['oauth_%s_request_token' % get_token_prefix(
                self.request_token_url)] = self.request_token
        return self.request_token