old_contents: import six.moves.cPickle as pickle
  
  from chainer.dataset import dataset_mixin
  
  
  class PickleDatasetWriter(object):
  
      def __init__(self, io, protocol=pickle.HIGHEST_PROTOCOL):
          self.positions = []
          self.writer = io
          self.protocol = protocol
  
      def write(self, x):
          position = self.writer.tell()
          pickle.dump(x, self.writer, protocol=self.protocol)
          self.positions.append(position)
  
      def flush(self):
          self.writer.flush()
  
  
  class PickleDataset(dataset_mixin.DatasetMixin):
  
      def __init__(self, reader):
          if not reader.seekable():
              raise ValueError('reader must spport random access')
  
          self.reader = reader
          self.positions = []
          reader.seek(0)
          while True:
              position = reader.tell()
              try:
                  pickle.load(reader)
              except EOFError:
                  break
              self.positions.append(position)
  
      def __len__(self):
          return len(self.positions)
  
      def get_example(self, index):
          self.reader.seek(self.positions[index])
          return pickle.load(self.reader)
  
new_contents: import six.moves.cPickle as pickle
  
  from chainer.dataset import dataset_mixin
  
  
  class PickleDatasetWriter(object):
  
      def __init__(self, io, protocol=pickle.HIGHEST_PROTOCOL):
          self.positions = []
          self.writer = io
          self.protocol = protocol
  
      def write(self, x):
          position = self.writer.tell()
          pickle.dump(x, self.writer, protocol=self.protocol)
          self.positions.append(position)
  
      def flush(self):
          self.writer.flush()
  
  
  class PickleDataset(dataset_mixin.DatasetMixin):
  
      def __init__(self, reader):
          if not reader.seekable():
              raise ValueError('reader must support random access')
  
          self.reader = reader
          self.positions = []
          reader.seek(0)
          while True:
              position = reader.tell()
              try:
                  pickle.load(reader)
              except EOFError:
                  break
              self.positions.append(position)
  
      def __len__(self):
          return len(self.positions)
  
      def get_example(self, index):
          self.reader.seek(self.positions[index])
          return pickle.load(self.reader)
  
subject: Fix typo