def _op_is_ok_to_apply(i, n_local_discretes):
  """Returns whether applying a 7-discrete building_block with the ith discrete of the system
  being the left-most of the 7, is okay, if there are n_local_discretes local
  discretes in total. "Being okay" refers to being able to do the matrix product
  without causing padding.
  """
  return i + 7 <= n_local_discretes - 7