code: def utilization(prev, curr, counters):
      
      busy_prop, idle_prop = counters
  
      pb = getattr(prev, busy_prop)
      pi = getattr(prev, idle_prop)
  
      cb = getattr(curr, busy_prop)
      ci = getattr(curr, idle_prop)
  
      db = minus(cb, pb)
      di = minus(ci, pi)
  
      return mul(div(db, add(db, di)), 100)
docs: calculate the utilization
  
      delta_busy = curr.busy - prev.busy
      delta_idle = curr.idle - prev.idle
      utilization = delta_busy / (delta_busy + delta_idle)
  
      :param prev: previous resource
      :param curr: current resource
      :param counters: list of two, busy ticks and idle ticks
      :return: value, NaN if invalid.