def add_user_permission(self, user_id, permission_obj):
headers = {<EOL>'<STR_LIT>': self.user_agent(),<EOL>'<STR_LIT:Content-Type>': self.content_type()<EOL>}<EOL>headers.update(self.headers())<EOL>url = self.portals_url()+'<STR_LIT>'.format(user_id)<EOL>r = requests.post(  url,<EOL>data=permission_obj,<EOL>headers=headers,<EOL>auth=self.auth())<EOL>if HTTP_STATUS.OK == r.status_code:<EOL><INDENT>return r.json()<EOL><DEDENT>else:<EOL><INDENT>print("<STR_LIT>".format(<EOL>r.status_code, r.reason))<EOL>r.raise_for_status()<EOL><DEDENT>
permission' param should be a string. 
                e.g. '[{"access":"d_u_list","oid":{"id":"1576946496","type":"Domain"}}]'

        http://docs.exosite.com/portals/#add-user-permission