title: Are special tokens [CLS] [SEP] absolutely necessary while fine tuning BERT?
body: <p>I am following the tutorial <a href="https://www.depends-on-the-definition.com/named-entity-recognition-with-bert/" rel="nofollow noreferrer">https://www.depends-on-the-definition.com/named-entity-recognition-with-bert/</a> to do Named Entity Recognition with BERT.</p>
  <p>While fine-tuning, before feeding the tokens to the model, the author does:</p>
  <pre><code>input_ids = pad_sequences([tokenizer.convert_tokens_to_ids(txt) for txt in tokenized_texts],
                            maxlen=MAX_LEN, dtype=&quot;long&quot;, value=0.0,
                            truncating=&quot;post&quot;, padding=&quot;post&quot;)
  </code></pre>
  <p>According to my tests, this doesn't add special tokens to the ids. So am I missing something or i it not always necessary to include [CLS] (101) [SEP] (102)?</p>