code: def add_phone_number(self, phone_number):
          
          sess = self._get_web_session()
  
          try:
              resp = sess.post('https://steamcommunity.com/steamguard/phoneajax',
                              data={
                                  'op': 'add_phone_number',
                                  'arg': phone_number,
                                  'checkfortos': 0,
                                  'skipvoip': 0,
                                  'sessionid': sess.cookies.get('sessionid', domain='steamcommunity.com'),
                                  },
                              timeout=15).json()
          except:
              return False
  
          return (resp or {}).get('success', False)
docs: Add phone number to account
  
          Then confirm it via :meth:`confirm_phone_number()`
  
          :param phone_number: phone number with country code
          :type  phone_number: :class:`str`
          :return: success (returns ``False`` on request fail/timeout)
          :rtype: :class:`bool`