docs: def expiration_maintenance(self):
          """ Decrement cell value if not zero
              This maintenance process need to executed each self.compute_refresh_time()
          """
          if self.cellarray[self.refresh_head] != 0:
              self.cellarray[self.refresh_head] -= 1
          self.refresh_head = (self.refresh_head + 1) % self.nbr_bits