docs: def _fill(self):
          """Fills bucket with accrued tokens since last fill."""
  
          right_now = time.time()
          time_diff = right_now - self._last_fill
          if time_diff < 0:
              return
  
          self._count = min(
              self._count + self._fill_rate * time_diff,
              self._capacity,
          )
          self._last_fill = right_now