code: public static FileSystem getWriterFileSystem(State state, int numBranches, int branchId)
        throws IOException {
      return HadoopUtils.getOptionallyThrottledFileSystem(WriterUtils.getWriterFS(state, numBranches, branchId), state);
    }
docs: Get a {@link FileSystem} object for the uri specified at {@link ConfigurationKeys#WRITER_FILE_SYSTEM_URI}.
  @throws IOException