def get_objective_bank_hierarchy(self, alias=None):
if alias is not None:<EOL><INDENT>url_path = self._urls.hierarchy(re.sub(r'<STR_LIT>', '<STR_LIT>', alias.lower()))<EOL><DEDENT>else:<EOL><INDENT>url_path = self._urls.hierarchy()<EOL><DEDENT>return self._get_request(url_path)<EOL>
Gets the hierarchy associated with this session.

        return: (osid.hierarchy.Hierarchy) - the hierarchy associated
                with this session
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        compliance: mandatory - This method must be implemented.