docs: def unpacked_contents(self):
          """
          :return:
          """
  
          from nbformat import read
  
          import msgpack
  
          if self.mime_type == 'text/plain':
              return self.contents.decode('utf-8')
          elif self.mime_type == 'application/msgpack':
              # FIXME: Note: I'm not sure that encoding='utf-8' will not break old data.
              # We need utf-8 to make python3 to work. (kazbek)
              # return msgpack.unpackb(self.contents)
              return msgpack.unpackb(self.contents, encoding='utf-8')
          else:
              return self.contents