BERTCGAForcaster Class

[sonqt]

Description

This PR introduces several enhancements and new features, including:

• Forecaster Class: Implements support for auto-encoding transformer models such as BERT, RoBERTa, SpanBERT, DeBERTa, and ELECTRA.
• New Metric for forecaster.summarize(): Adds an additional evaluation metric to improve summarization capabilities.
• BERTCGAModel Class: Implements a new model class specifically designed for forecasting with BERT-based architectures.
• Jupyter Notebooks:
  • Demonstration notebooks showcasing how to use BERTCGAModel.
  • Notebooks for reproducing the performance results reported in the paper.
• Enhanced Download Configuration: Modifies download_config to enable downloading fine-tuned BERT-base and RoBERTa-large models from the Zissou server.