Custom errors and BatchSizeError (#13184)
* Adding custom errors and BatchSizeError for GPT2
* Adding custom errors and BatchSizeError for GPT2
* Changing Exception to BaseException
* Exception
* Adding args to Custom Exception
* Adding args to Custom Exception
* Changing from BaseException to Exception
* Changing Conditional loop syntax
* Adding Copyright info
* Handling check_code_quality
* Handling check_code_quality pt2
* Handling check_code_quality pt3
* Handling check_code_quality pt4
* Handling check_code_quality pt5
* Handling check_code_quality pt6
* Handling check_code_quality pt6
* Using black for check_code_quality
* sorting import style
* Changing
* Changing
* verified through style_doc.py
* verified through style_doc.py
* applying isort
* Removing indentation
* Changing
* Changing
* Changing
* Used ValueError
* Using ValueError
* Reformatted Style doc
* Using style doc on modeling_gp2.py
* Adding indentation
* Changing