Get the authorization URL to redirect the user

def get_authorization_url(self):
        """Get the authorization URL to redirect the user"""
        url = self._get_oauth_url('authenticate')
        query = {
            'client_id': self._client_id,
            'response_type': 'code',
            'redirect_uri': self.callback
        }
        query_str = self.urlencode(query)

        return url + '?' + query_str