class_docstr: Class which encapsulates logit of the master.
docstr: Saves errors for given work pieces into file.
  
  Args:
    work: instance of either AttackWorkPieces or DefenseWorkPieces
    output_file: name of the output file
code: def _export_work_errors(self, work, output_file):
      """Saves errors for given work pieces into file.
  
      Args:
        work: instance of either AttackWorkPieces or DefenseWorkPieces
        output_file: name of the output file
      """
      errors = set()
      for v in itervalues(work.work):
          if v["is_completed"] and v["error"] is not None:
              errors.add(v["error"])
      with open(output_file, "w") as f:
          for e in sorted(errors):
              f.write(e)
              f.write("\n")
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import argparse
  import collections
  from collections import defaultdict
  import csv
  from io import BytesIO
  import logging
  import os
  import pickle
  import random
  import time
  from six import iteritems
  from six import iterkeys
  from six import itervalues
  from six.moves import input
  import eval_lib
label_desc: Use image node_id 10 for calling the EvaluationMaster obj's underlying member method code with example usage: obj._export_work_errors(work, output_file) without return types