Why does PEGASUS generate summaries with <n> tags?

Why does PEGASUS generate summaries with tags?

Here is how a have initialized the model and generate summaries:
from transformers import PegasusForConditionalGeneration, PegasusTokenizerFast, PegasusConfig

import torch

torch_device = 'cuda' if torch.cuda.is_available() else 'cpu'

pegasus_model = PegasusForConditionalGeneration.from_pretrained('google/pegasus-pubmed').to(torch_device)

pegasus_tokenizer = PegasusTokenizerFast.from_pretrained('google/pegasus-pubmed', max_position_embeddings=2048)

def pegasus_summarization(article):
  batch = pegasus_tokenizer.prepare_seq2seq_batch([article], truncation=True, padding='longest', max_target_length=250, return_tensors='pt').to(torch_device)
  translated = pegasus_model.generate(**batch)
  tgt_text = pegasus_tokenizer.batch_decode(translated, skip_special_tokens=True)
  return tgt_text[0]

And here is the resulting summary:

anxiety is the most prominent and prevalent mood disorder in parkinson’s disease ( pd ) ; however, little is known about the relationship between anxiety and cognition in pd. <n> the aim of this study was to examine the influence of anxiety on cognition in pd by directly comparing groups of pd patients with and without anxiety while excluding depression. <n> we hypothesized that pd patients with anxiety would show impairments in attentional set - shifting and working memory compared to pd patients without anxiety.

I used pegasus in October last year, but was not a problem then. Maybe it is something that came with the v4.0.0 release of transformers?

I found others that have experienced the same (text2slide/pegasus.py at 8af85b423f68b399b88292c8a08c2cbf5a744ea1 · eeic-ai-01/text2slide · GitHub) ref the regex substitute of <n>-tags.

Appreciate all answers!