code: public static void clearSnapshot(String snapshotName, String keyspace)
      {
          List<File> snapshotDirs = Directories.getKSChildDirectories(keyspace);
          Directories.clearSnapshot(snapshotName, snapshotDirs);
      }
docs: Clear all the snapshots for a given keyspace.
  
  @param snapshotName the user supplied snapshot name. It empty or null,
  all the snapshots will be cleaned