code: def _check_pretrained_file_names(cls, pretrained_file_name):
          
  
          embedding_name = cls.__name__.lower()
          if pretrained_file_name not in cls.pretrained_file_name_sha1:
              raise KeyError('Cannot find pretrained file %s for token embedding %s. Valid '
                             'pretrained files for embedding %s: %s' %
                             (pretrained_file_name, embedding_name, embedding_name,
                              ', '.join(cls.pretrained_file_name_sha1.keys())))
docs: Checks if a pre-trained token embedding file name is valid.
  
  
          Parameters
          ----------
          pretrained_file_name : str
              The pre-trained token embedding file.