Fix part of #7427 Add args, raises in exp_domain.py (#8288)
Fix part of #7427 Add args, raises in exp_domain.py (#8288)

* Fix part of #7427

Fixes part of #7427: Add args, raises in exp_domain.py

* Add docstring for _convert_v29_dict_to_v30_dict

* Add blank line above this heading

Added the missing blank lines before Args and Returns in docstring

kevinlee12/oppia,prasanna08/oppia,oppia/oppia,prasanna08/oppia,oppia/oppia,oppia/oppia,brianrodri/oppia,kevinlee12/oppia,brianrodri/oppia,brianrodri/oppia,oppia/oppia,prasanna08/oppia,kevinlee12/oppia,brianrodri/oppia,prasanna08/oppia,prasanna08/oppia,kevinlee12/oppia,brianrodri/oppia,kevinlee12/oppia,oppia/oppia