e. This is only called if <code>next ()</code> has previously returned <code>Some x</code> and <code>x</code> was sent to a worker.</p></td></tr><tr id="type-t.next" class="anchored"><td class="def field"><a href="#type-t.next" class="anchor"></a><code>next : unit <span>&#45;&gt;</span> <span><span class="type-var">'a</span> option</span>;</code></td><td class="doc"><p><code>next ()</code> generates the next work item. If <code>is_empty ()</code> is true then <code>next ()</code> must return <code>None</cod