I am trying to get the shap values for the masked language modeling task using transformer. I get the error KeyError: 'label' for the code where I input a single data sample to get the explanation. My complete code and error trace are as follows:
import transformers
import shap
from transformers import RobertaTokenizer, RobertaForMaskedLM, pipeline
import torch
model = RobertaForMaskedLM.from_pretrained('microsoft/codebert-base-mlm')
tokenizer = RobertaTokenizer.from_pretrained('microsoft/codebert-base-mlm')
code_example = "if (x <mask> 10)"
fill_mask = pipeline('fill-mask', model=model, tokenizer=tokenizer)
explainer = shap.Explainer(fill_mask)
shap_values = explainer(['x {tokenizer.mask_token} 10'])
Following is the error trace
KeyError Traceback (most recent call last)
[<ipython-input-12-bb3832d1772d>](https://localhost:8080/#) in <module>
6 # explain the model on two sample inputs
7 explainer = shap.Explainer(fill_mask)
----> 8 shap_values = explainer(['x {tokenizer.mask_token} 10'])
9 print(shap_values)
10 # visualize the first prediction's explanation for the POSITIVE output class
5 frames
[/usr/local/lib/python3.7/dist-packages/shap/explainers/_partition.py](https://localhost:8080/#) in __call__(self, max_evals, fixed_context, main_effects, error_bounds, batch_size, outputs, silent, *args)
136 return super().__call__(
137 *args, max_evals=max_evals, fixed_context=fixed_context, main_effects=main_effects, error_bounds=error_bounds, batch_size=batch_size,
--> 138 outputs=outputs, silent=silent
139 )
140
[/usr/local/lib/python3.7/dist-packages/shap/explainers/_explainer.py](https://localhost:8080/#) in __call__(self, max_evals, main_effects, error_bounds, batch_size, outputs, silent, *args, **kwargs)
266 row_result = self.explain_row(
267 *row_args, max_evals=max_evals, main_effects=main_effects, error_bounds=error_bounds,
--> 268 batch_size=batch_size, outputs=outputs, silent=silent, **kwargs
269 )
270 values.append(row_result.get("values", None))
[/usr/local/lib/python3.7/dist-packages/shap/explainers/_partition.py](https://localhost:8080/#) in explain_row(self, max_evals, main_effects, error_bounds, batch_size, outputs, silent, fixed_context, *row_args)
159 # if not fixed background or no base value assigned then compute base value for a row
160 if self._curr_base_value is None or not getattr(self.masker, "fixed_background", False):
--> 161 self._curr_base_value = fm(m00.reshape(1, -1), zero_index=0)[0] # the zero index param tells the masked model what the baseline is
162 f11 = fm(~m00.reshape(1, -1))[0]
163
[/usr/local/lib/python3.7/dist-packages/shap/utils/_masked_model.py](https://localhost:8080/#) in __call__(self, masks, zero_index, batch_size)
65
66 else:
---> 67 return self._full_masking_call(masks, batch_size=batch_size)
68
69 def _full_masking_call(self, masks, zero_index=None, batch_size=None):
[/usr/local/lib/python3.7/dist-packages/shap/utils/_masked_model.py](https://localhost:8080/#) in _full_masking_call(self, masks, zero_index, batch_size)
142
143 joined_masked_inputs = tuple([np.concatenate(v) for v in all_masked_inputs])
--> 144 outputs = self.model(*joined_masked_inputs)
145 _assert_output_input_match(joined_masked_inputs, outputs)
146 all_outputs.append(outputs)
[/usr/local/lib/python3.7/dist-packages/shap/models/_transformers_pipeline.py](https://localhost:8080/#) in __call__(self, strings)
33 val = [val]
34 for obj in val:
---> 35 output[i, self.label2id[obj["label"]]] = sp.special.logit(obj["score"]) if self.rescale_to_logits else obj["score"]
36 return output
KeyError: 'label'