'Add a character attribute to a copy of this formatting state.
@param **kw: An optional attribute name and value can be provided with
a keyword argument.
@return: A formatting state instance with the new attribute.
@see: L{DefaultFormattingState._withAttribute}.'

@deprecated(Version('Twisted', 13, 1, 0))
def wantOne(self, **kw):

    (k, v) = kw.popitem()
    return self._withAttribute(k, v)
