code: def get_subword_prefix(self):
      return self.SUBWORD_PREFIX
  
file_path: nlpaug/nlpaug/model/lang_models/roberta.py
imports: import logging
  from nlpaug.model.lang_models import LanguageModels
  from nlpaug.util.selection.filtering import *
label_desc: Use image node_id 7 for calling the Roberta obj's underlying member method code with example usage: obj.get_subword_prefix() and returns: self