Add BioGPTForSequenceClassification (#22253)

* added BioGptForSequenceClassification

* added source of copied code

* typo

* Format code with black

* Update comments for copied code

* Remove code copy comment

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* Fix failing tests

* Update code copied from comments

* Fix code quality

* Update src/transformers/models/biogpt/modeling_biogpt.py

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* Fix lint error

* Update src/transformers/models/biogpt/modeling_biogpt.py

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* Rename model to biogpt for consistency

* Add PipelineTesterMixin to test_modeling_biogpt.py

* Apply suggestions from code review

Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

* Resolve merge confict

---------

Co-authored-by: Guillem García Subies <37592763+GuillemGSubies@users.noreply.github.com>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

docs/source/en/model_doc/biogpt.mdx

@@ -54,8 +54,15 @@ This model was contributed by [kamalkraj](https://huggingface.co/kamalkraj). The
 
 [[autodoc]] BioGptForCausalLM
     - forward
+
     
 ## BioGptForTokenClassification
 
 [[autodoc]] BioGptForTokenClassification
+    - forward
+
+
+## BioGptForSequenceClassification
+
+[[autodoc]] BioGptForSequenceClassification
     - forward