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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):
 """ Fetch a request token from `self.request_token_url`. """

        
        params = {
            'oauth_callback': self.get_callback_url()
        }
        
        
        response, content = self.client().request(self.request_token_url,
            "POST", body=urllib.urlencode(params))
        
        content = smart_unicode(content)

        if not response['status'] == '200':
            raise OAuthError(_(
                u"Invalid status code %s while obtaining request token from %s: %s") % (
                    response['status'], self.request_token_url, content))
        
        token = dict(urlparse.parse_qsl(content))
        
        return oauth.Token(token['oauth_token'], token['oauth_token_secret'])