def set_license(self, license_=None):
pass<EOL>
Sets the license.

        arg:    license (string): the new license
        raise:  InvalidArgument - ``license`` is invalid
        raise:  NoAccess - ``Metadata.isReadOnly()`` is ``true``
        raise:  NullArgument - ``license`` is ``null``
        *compliance: mandatory -- This method must be implemented.*