ignore it, solved
encoding = self.tokenizer.encode_plus(

      [author,

      source,

      title,

      content],

      add_special_tokens=True,

      max_length=self.max_len,

      return_token_type_ids=False,

      pad_to_max_length=True,

      return_attention_mask=True,

      return_tensors='pt',

    )