code: def render_delta(d):
      
      s = '' if d >= 0 else '-'
      d = abs(d)
  
      for unit in _SORTED_UNITS:
          span = __timedelta_millis(unit[1])
          if d >= span:
              count = int(d // span)
              s += '{0}{1}'.format(count, unit[0])
              d -= count * span
  
      if d or not s:
          s += str(d)
  
      return s
docs: Render the given delta (in milliseconds) as a human-readable delta.