text: '''
  Defines the set of symbols used in text input to the model.
  
  The default is a set of ASCII characters that works well for English or text that has been run
  through Unidecode. For other data, you can modify _characters. See TRAINING_DATA.md for details.
  '''
  from text import cmudict
  
  _pad        = '_'
  _eos        = '~'
  _characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!\'(),-.:;? '
  
  # Prepend "@" to ARPAbet symbols to ensure uniqueness (some are the same as uppercase letters):
  _arpabet = ['@' + s for s in cmudict.valid_symbols]
  
  # Export all symbols:
  symbols = [_pad, _eos] + list(_characters) + _arpabet
  