code: def CopyTextToLabel(cls, text, prefix=''):
      
      text = '{0:s}{1:s}'.format(prefix, text)
      return cls._INVALID_LABEL_CHARACTERS_REGEX.sub('_', text)
docs: Copies a string to a label.
  
      A label only supports a limited set of characters therefore
      unsupported characters are replaced with an underscore.
  
      Args:
        text (str): label text.
        prefix (Optional[str]): label prefix.
  
      Returns:
        str: label.