LongModelForMaskedLM should inherit from MODEL

[eric00hahn]

Hi,
in scripts/run_long_mlm.py the class LongModelForMaskedLM should inherit from MODEL

class LongModelForMaskedLM(MODEL):
     def __init__(self, config):
         super().__init__(config)
         print(f"\n{color.YELLOW}Converting models to Longformer is currently only tested for RoBERTa like architectures.{color.END}")
         for i, layer in enumerate(self.roberta.encoder.layer):
             layer.attention.self = LongModelSelfAttention(config, layer_id=i)

instead of

class LongModelForMaskedLM():
     def __init__(self, config):
         super().__init__(config)
         print(f"\n{color.YELLOW}Converting models to Longformer is currently only tested for RoBERTa like architectures.{color.END}")
         for i, layer in enumerate(self.roberta.encoder.layer):
             layer.attention.self = LongModelSelfAttention(config, layer_id=i)

Also I think the regexes in

 def is_roberta_based_model(model_name: str) -> str:
     """Validate if the model to pre-train is of roberta architecture."""
     if re.search("(?i)(xlm)\D(roberta)", model_name) == 'xlm-roberta':
         model_name = 'xlm-roberta'
     elif re.search("(?i)(roberta)", model_name) == 'roberta':
         model_name = 'roberta'
     else:
         model_name = 'none'
     return model_name

are broken because for 'xlm-roberta-base' the function returns 'none'.