code: def calculate_perf_counter_100ns_queuelen_type(previous, current, property_name):
      
      n0 = previous[property_name]
      n1 = current[property_name]
      d0 = previous["Timestamp_Sys100NS"]
      d1 = current["Timestamp_Sys100NS"]
      if n0 is None or n1 is None:
          return
  
      return (n1 - n0) / (d1 - d0)
docs: PERF_COUNTER_100NS_QUEUELEN_TYPE
  
      Average length of a queue to a resource over time in 100 nanosecond units.
  
      https://msdn.microsoft.com/en-us/library/aa392905(v=vs.85).aspx
  
      Formula (n1 - n0) / (d1 - d0)