numTreeCacheEntries use for what in FPGrowthDriver

[myn <my...@163.com>]

this option  I can`t found any where to be used . what is was do for
    Option treeCacheOpt = obuilder.withLongName("numTreeCacheEntries").withArgument(
      abuilder.withName("numTreeCacheEntries").withMinimum(1).withMaximum(1).create()).withDescription(
      "(Optional) Number of entries in the tree cache to prevent duplicate tree building. "
          + "(Warning) a first level conditional FP-Tree might consume a lot of memory, "
          + "so keep this value small, but big enough to prevent duplicate tree building. "
          + "Default Value:5 Recommended Values: [5-10]").withShortName("tc").create();
 
....
 
  if (cmdLine.hasOption(treeCacheOpt)) {
        String numTreeCacheString = (String) cmdLine.getValue(treeCacheOpt);
        params.set("treeCacheSize", numTreeCacheString);
      }