code: def _chunk_setitem(self, chunk_coords, chunk_selection, value, fields=None):
          
  
          if self._synchronizer is None:
              # no synchronization
              lock = nolock
          else:
              # synchronize on the chunk
              ckey = self._chunk_key(chunk_coords)
              lock = self._synchronizer[ckey]
  
          with lock:
              self._chunk_setitem_nosync(chunk_coords, chunk_selection, value,
                                         fields=fields)
docs: Replace part or whole of a chunk.
  
          Parameters
          ----------
          chunk_coords : tuple of ints
              Indices of the chunk.
          chunk_selection : tuple of slices
              Location of region within the chunk.
          value : scalar or ndarray
              Value to set.