code: def _build(self, items, chunk_size=10000):
          
          _log.debug("_build, chunk_size={:d}".format(chunk_size))
          n, i = 0, 0
          for i, item in enumerate(items):
              if i == 0:
                  _log.debug("_build, first item")
              if 0 == (i + 1) % chunk_size:
                  if self._seq:
                      self._run(0)
                  else:
                      self._run_parallel_fn()  # process the chunk
                  if self._status.has_failures():
                      break
                  n = i + 1
              self._queue.put(item)
          # process final chunk
          if self._seq:
              self._run(0)
          else:
              self._run_parallel_fn()
          if not self._status.has_failures():
              n = i + 1
          return n
docs: Build the output, in chunks.
  
          :return: Number of items processed
          :rtype: int