@utilities.arguments_not_none<EOL><INDENT>def set_level(self, grade_id):<DEDENT>
<EOL>if self.get_level_metadata().is_read_only():<EOL><INDENT>raise errors.NoAccess()<EOL><DEDENT>if not self._is_valid_id(grade_id):<EOL><INDENT>raise errors.InvalidArgument()<EOL><DEDENT>self._my_map['<STR_LIT>'] = str(grade_id)<EOL>
Sets the level of difficulty expressed as a ``Grade``.

        arg:    grade_id (osid.id.Id): the grade level
        raise:  InvalidArgument - ``grade_id`` is invalid
        raise:  NoAccess - ``Metadata.isReadOnly()`` is ``true``
        *compliance: mandatory -- This method must be implemented.*