There doesn’t seem to be any padding occurring here:
     train_dataset = dataset.shard(10, 1)

    train_dataset.set_format(columns=['text'])

    train_dataset.cleanup_cache_files()

    encoded_dataset = train_dataset.map(lambda examples: tokenizer(examples['text'], padding=True))

    encoded_dataset[:1]

    {'attention_mask': [[1, 1, 1, 1, 1, 1, 1]],
     'input_ids': [[101, 1714, 22233, 21365, 4515, 8618, 102]],
     'text': ['free instagram followers '],
     'token_type_ids': [[0, 0, 0, 0, 0, 0, 0]]}

What am I missing?