code: def add_member(self, host_name, hostgroup_name):
          
          hostgroup = self.find_by_name(hostgroup_name)
          if not hostgroup:
              hostgroup = Hostgroup({'hostgroup_name': hostgroup_name,
                                     'alias': hostgroup_name,
                                     'members': host_name})
              self.add(hostgroup)
          else:
              hostgroup.add_members(host_name)
docs: Add a host string to a hostgroup member
          if the host group do not exist, create it
  
          :param host_name: host name
          :type host_name: str
          :param hostgroup_name:hostgroup name
          :type hostgroup_name: str
          :return: None