<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_rsa_key(self, username):
 """Get rsa key for a given username :param username: username :type username: :class:`str` :return: json response :rtype: :class:`dict` :raises HTTPError: any problem with http request, timeouts, 5xx, 4xx etc """

        try:
            resp = self.session.post('https://steamcommunity.com/login/getrsakey/',
                                     timeout=15,
                                     data={
                                         'username': username,
                                         'donotchache': int(time() * 1000),
                                         },
                                     ).json()
        except requests.exceptions.RequestException as e:
            raise HTTPError(str(e))

        return resp