@abc.abstractmethod<EOL><INDENT>def get_proficiency_objective_bank_session(self):<DEDENT>
return<EOL>
Gets the ``OsidSession`` to lookup proficiency/objective bank mappings.

        :return: a ``ProficiencyObjectiveBankSession``
        :rtype: ``osid.learning.ProficiencyObjectiveBankSession``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_proficiency_objective_bank()`` is ``false``

        *compliance: optional -- This method must be implemented if
        ``supports_proficiency_objective_bank()`` is ``true``.*