public static boolean skipSkewedDirectory(Boolean bool) {
    if (bool == null) {
      return false;
    }
    return !bool.booleanValue();
  }
Decide if pruner skips the skewed directory
Input: if the skewed value matches the expression tree
Ouput: if pruner should skip the directory represented by the skewed value
If match result is unknown(null) or true, pruner doesn't skip the directory
If match result is false, pruner skips the dir.
@param bool
         if the skewed value matches the expression tree
@return
ql/src/java/org/apache/hadoop/hive/ql/optimizer/listbucketingpruner/ListBucketingPrunerUtils.java