code: def _operations_list(self, ops_filter, max_tasks, page_size, page_token):
      
  
      # We are not using the documented default page size of 256,
      # nor allowing for the maximum page size of 2048 as larger page sizes
      # currently cause the operations.list() API to return an error:
      # HttpError 429 ... Resource has been exhausted (e.g. check quota).
      max_page_size = 128
  
      # Set the page size to the smallest (non-zero) size we can
      page_size = min(sz for sz in [page_size, max_page_size, max_tasks] if sz)
  
      # Execute operations.list() and return all of the dsub operations
      api = self._service.projects().operations().list(
          name='projects/{}/operations'.format(self._project),
          filter=ops_filter,
          pageToken=page_token,
          pageSize=page_size)
      response = google_base.Api.execute(api)
  
      return [
          GoogleOperation(op)
          for op in response.get('operations', [])
          if google_v2_operations.is_dsub_operation(op)
      ], response.get('nextPageToken')
docs: Gets the list of operations for the specified filter.
  
      Args:
        ops_filter: string filter of operations to return
        max_tasks: the maximum number of job tasks to return or 0 for no limit.
        page_size: the number of operations to requested on each list operation to
          the pipelines API (if 0 or None, the API default is used)
        page_token: page token returned by a previous _operations_list call.
  
      Returns:
        Operations matching the filter criteria.