simpletransformers: ImportError: cannot import name 'ElectraForMaskedLM'

Describe the bug

ImportError                               Traceback (most recent call last)
<ipython-input-21-c3e03203b6fb> in <module>
----> 1 from simpletransformers.classification import MultiLabelClassificationModel

/opt/conda/lib/python3.6/site-packages/simpletransformers/classification/__init__.py in <module>
      1 from simpletransformers.classification.classification_model import ClassificationModel
----> 2 from simpletransformers.classification.multi_label_classification_model import MultiLabelClassificationModel
      3 from simpletransformers.classification.multi_modal_classification_model import MultiModalClassificationModel

/opt/conda/lib/python3.6/site-packages/simpletransformers/classification/multi_label_classification_model.py in <module>
      6 
      7 from simpletransformers.classification import ClassificationModel
----> 8 from simpletransformers.custom_models.models import (
      9     BertForMultiLabelSequenceClassification,
     10     RobertaForMultiLabelSequenceClassification,

/opt/conda/lib/python3.6/site-packages/simpletransformers/custom_models/models.py in <module>
     12 from transformers import FlaubertModel
     13 from transformers.configuration_xlm_roberta import XLMRobertaConfig
---> 14 from transformers import ElectraForMaskedLM, ElectraForPreTraining
     15 from torch.nn import BCEWithLogitsLoss
     16 

ImportError: cannot import name 'ElectraForMaskedLM'

To Reproduce from simpletransformers.classification import MultiLabelClassificationModel

Expected behavior Successful Import

Desktop (please complete the following information):

• Ubuntu 16.04
• simpletransformers-0.24.1