code: def list_machines(self, project_name, group_name, offset=0, size=100):
          
  
          # need to use extended method to get more
          if int(size) == -1 or int(size) > MAX_LIST_PAGING_SIZE:
              return list_more(self.list_machines, int(offset), int(size), MAX_LIST_PAGING_SIZE, project_name, group_name)
  
          headers = {}
          params = {}
          resource = "/machinegroups/" + group_name + "/machines"
          params['offset'] = str(offset)
          params['size'] = str(size)
          (resp, header) = self._send("GET", project_name, None, resource, params, headers)
          return ListMachinesResponse(resp, header)
docs: list machines in a machine group
          Unsuccessful opertaion will cause an LogException.
  
          :type project_name: string
          :param project_name: the Project name 
          
          :type group_name: string
          :param group_name: the group name to list
  
          :type offset: int
          :param offset: the offset of all group name
  
          :type size: int
          :param size: the max return names count, -1 means all
  
          :return: ListMachinesResponse
          
          :raise: LogException