code: def _initDevClasses(self):
          
          self._devClassTree = {}
          self._partitionTree = {}
          self._mapDevType = {}
          basedevs = []
          otherdevs = []
          if self._mapMajorDevclass is None:
              self._initBlockMajorMap()
          for dev in self._diskStats:
              stats = self._diskStats[dev]
              devclass = self._mapMajorDevclass.get(stats['major'])
              if devclass is not None:
                  devdir = os.path.join(sysfsBlockdevDir, dev)
                  if os.path.isdir(devdir):
                      if not self._devClassTree.has_key(devclass):
                          self._devClassTree[devclass] = []
                      self._devClassTree[devclass].append(dev)
                      self._mapDevType[dev] = devclass
                      basedevs.append(dev)
                  else:
                      otherdevs.append(dev)
          basedevs.sort(key=len, reverse=True)
          otherdevs.sort(key=len, reverse=True)
          idx = 0
          for partdev in otherdevs:
              while len(basedevs[idx]) > partdev:
                  idx += 1 
              for dev in basedevs[idx:]:
                  if re.match("%s(\d+|p\d+)$" % dev, partdev):
                      if not self._partitionTree.has_key(dev):
                          self._partitionTree[dev] = []
                      self._partitionTree[dev].append(partdev)
                      self._mapDevType[partdev] = 'part'
docs: Sort block devices into lists depending on device class and 
          initialize device type map and partition map.