def set_difficulty(self, difficulty):
if not is_string(difficulty):<EOL><INDENT>raise InvalidArgument('<STR_LIT>')<EOL><DEDENT>if difficulty.lower() not in ['<STR_LIT>', '<STR_LIT>', '<STR_LIT>']:<EOL><INDENT>raise InvalidArgument('<STR_LIT>')<EOL><DEDENT>self.my_osid_object_form._my_map['<STR_LIT>']['<STR_LIT>']['<STR_LIT:text>'] = difficulty<EOL>
stub