<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def addUser(self, invitationList, subject, html):
 """ adds a user without sending an invitation email Inputs: invitationList - InvitationList class used to add users without sending an email subject - email subject html - email message sent to users in invitation list object """

        url = self._url + "/invite"
        params = {"f" : "json"}
        if isinstance(invitationList, parameters.InvitationList):
            params['invitationList'] = invitationList.value()
        params['html'] = html
        params['subject'] = subject
        return self._post(url=url,
                             param_dict=params,
                             securityHandler=self._securityHandler,
                             proxy_url=self._proxy_url,
                             proxy_port=self._proxy_port)