It's necessary for placing the <code>setno is None and n_evokeds > 1</code> check in <code>read_evoked</code> rather than the initialization <code>Evoked</code>.  This, in turn, is necessary to allow both <code>read_evoked</code> and <code>read_evokeds</code> to work properly, i.e. fail when <code>setno is None and n_evokeds > 1</code> for <code>read_evoked</code> but return all evokeds for <code>read_evokeds</code>.