AttributeError: 'GPT2TokenizerFast' object has no attribute 'r1c1'

--- VLM Config ---
VLMConfig(vit_hidden_dim=768, vit_inter_dim=3072, vit_patch_size=16, vit_img_size=512, vit_n_heads=12, vit_dropout=0.0, vit_n_blocks=12, vit_ln_eps=1e-06, vit_cls_flag=False, vit_model_type='modelhub/google/siglip2-base-patch16-512', lm_hidden_dim=960, lm_inter_dim=2560, lm_rms_eps=1e-05, lm_re_base=100000, lm_max_position_embeddings=8192, lm_base_vocab_size=49152, extra_token_amount=17, lm_vocab_size=49169, lm_n_heads=15, lm_n_kv_heads=5, lm_dropout=0.0, lm_n_blocks=32, lm_attn_scaling=1.0, lm_max_length=1024, lm_use_tokens=False, lm_tie_weights=True, lm_model_type='modelhub/HuggingFaceTB/SmolLM2-360M-Instruct', lm_tokenizer='modelhub/HuggingFaceTB/cosmo2-tokenizer', lm_chat_template="{% for message in messages %}{{'<|im_start|>' + message['role'] + '\n' + message['content'] + '<|im_end|>' + '\n'}}{% endfor %}{% if add_generation_prompt %}{{ '<|im_start|>assistant\n' }}{% endif %}", mp_pixel_shuffle_factor=4, mp_image_token_length=64, max_img_size=1024, vlm_extra_tokens={'image_token': '<|image|>', 'r1c1': '<row_1_col_1>', 'r1c2': '<row_1_col_2>', 'r1c3': '<row_1_col_3>', 'r1c4': '<row_1_col_4>', 'r2c1': '<row_2_col_1>', 'r2c2': '<row_2_col_2>', 'r2c3': '<row_2_col_3>', 'r2c4': '<row_2_col_4>', 'r3c1': '<row_3_col_1>', 'r3c2': '<row_3_col_2>', 'r3c3': '<row_3_col_3>', 'r3c4': '<row_3_col_4>', 'r4c1': '<row_4_col_1>', 'r4c2': '<row_4_col_2>', 'r4c3': '<row_4_col_3>', 'r4c4': '<row_4_col_4>'}, vlm_load_backbone_weights=True, vlm_checkpoint_path='checkpoints', hf_repo_name='nanoVLM')
--- Train Config ---
TrainConfig(lr_mp=0.00512, lr_backbones=5e-05, data_cutoff_idx=None, val_ratio=0.025, batch_size=8, gradient_accumulation_steps=8, max_grad_norm=1.0, eval_in_epochs=True, eval_interval=800, stats_log_interval=200, max_training_steps=5000, max_images_per_example=4, max_images_per_knapsack=18, max_sample_length=1024, compile=False, resume_from_vlm_checkpoint=False, train_dataset_path='datasets/HuggingFaceM4/the_cauldron', train_dataset_name=('all',), wandb_entity='HuggingFace', log_wandb=False, use_lmms_eval=True, lmms_eval_tasks='mmstar,mmmu,ocrbench,textvqa', lmms_eval_limit=2000, lmms_eval_batch_size=128)
1111111111111111111111111111tokenizer_init_kwargs: {'use_fast': True, 'extra_special_tokens': {'image_token': '<|image|>', 'r1c1': '<row_1_col_1>', 'r1c2': '<row_1_col_2>', 'r1c3': '<row_1_col_3>', 'r1c4': '<row_1_col_4>', 'r2c1': '<row_2_col_1>', 'r2c2': '<row_2_col_2>', 'r2c3': '<row_2_col_3>', 'r2c4': '<row_2_col_4>', 'r3c1': '<row_3_col_1>', 'r3c2': '<row_3_col_2>', 'r3c3': '<row_3_col_3>', 'r3c4': '<row_3_col_4>', 'r4c1': '<row_4_col_1>', 'r4c2': '<row_4_col_2>', 'r4c3': '<row_4_col_3>', 'r4c4': '<row_4_col_4>'}, 'chat_template': "{% for message in messages %}{{'<|im_start|>' + message['role'] + '\n' + message['content'] + '<|im_end|>' + '\n'}}{% endfor %}{% if add_generation_prompt %}{{ '<|im_start|>assistant\n' }}{% endif %}"}
------------------------lm_tokenizer: modelhub/HuggingFaceTB/cosmo2-tokenizer
Loading from backbone weights
Successfully loaded modelhub/google/siglip2-base-patch16-512 weights from safetensors. Model has 86,433,024 parameters.
Extending token embeddings from torch.Size([49152, 960]) to torch.Size([49169, 960])
Initialized 17 new token embeddings
Successfully loaded modelhub/HuggingFaceTB/SmolLM2-360M-Instruct weights from safetensors. Model has 361,837,440 parameters.
nanoVLM initialized with 460,066,944 parameters
Training summary: 607 samples, 75 batches/epoch, batch size 64
Validation summary: 60 samples, 7 batches/epoch, batch size 64
Using device: cuda
**********************tokenizer: GPT2TokenizerFast(name_or_path='modelhub/HuggingFaceTB/cosmo2-tokenizer', vocab_size=49152, model_max_length=1000000000000000019884624838656, is_fast=True, padding_side='right', truncation_side='right', special_tokens={'bos_token': '<|endoftext|>', 'eos_token': '<|endoftext|>', 'unk_token': '<|endoftext|>', 'pad_token': '<|endoftext|>', 'additional_special_tokens': ['<|endoftext|>', '<|im_start|>', '<|im_end|>', '<repo_name>', '', '<file_sep>', '', '<gh_stars>', '<issue_start>', '<issue_comment>', '<issue_closed>', '<jupyter_start>', '<jupyter_text>', '<jupyter_code>', '<jupyter_output>', '<jupyter_script>', '<empty_output>']}, clean_up_tokenization_spaces=False), added_tokens_decoder={
0: AddedToken("<|endoftext|>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
1: AddedToken("<|im_start|>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
2: AddedToken("<|im_end|>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
3: AddedToken("<repo_name>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
4: AddedToken("", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
5: AddedToken("<file_sep>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
6: AddedToken("", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
7: AddedToken("<gh_stars>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
8: AddedToken("<issue_start>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
9: AddedToken("<issue_comment>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
10: AddedToken("<issue_closed>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
11: AddedToken("<jupyter_start>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
12: AddedToken("<jupyter_text>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
13: AddedToken("<jupyter_code>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
14: AddedToken("<jupyter_output>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
15: AddedToken("<jupyter_script>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
16: AddedToken("<empty_output>", rstrip=False, lstrip=False, single_word=False, normalized=False, special=True),
}

Start by tracing tokenizer initialization around the logged tokenizer_init_kwargs and the GPT2TokenizerFast instance, focusing on how the r1c1 extra token is registered. Confirm the failure in the training initialization path and consider the issue done when all configured extra tokens are available without the AttributeError.