-unresolved">Base</span>.option</span></span></code></div></div><div class="odoc-spec"><div class="spec value" id="val-ext_var_or_none" class="anchored"><a href="#val-ext_var_or_none" class="anchor"></a><code><span><span class="keyword">val</span> ext_var_or_none : <span><a href="#type-term">term</a> <span class="arrow">&#45;&gt;</span></span> <span><span><a href="#type-variable">variable</a> <span class="xref-unresolved">Base</span>.list</span> <span class="xref-unresolved">Base</span>.option</span></span>