Longformer model does not return pooler_output

I fine-tuned a Longfromer model and then I made a prediction using outputs = model(**batch, output_hidden_states=True). But when I tried to access the pooler_output using outputs.pooler_output, it returns None. I also checked the keys using outputs.keys(), and it returns: odict_keys([‘last_hidden_state’, ‘hidden_states’]). Am I forgetting to set a flag or something?