de never throws an error:</p>
<div class="sourceCode" id="cb2"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span class="va">sess</span> <span class="op">&lt;-</span> <span class="va">tf</span><span class="op">$</span><span class="fu">Session</span><span class="op">(</span><span class="op">)</span>
<span class="va">x</span> <span class="op">&lt;-</span> <span class="va">tf</span><span class="op">$</span><span class="fu">constant</span><span class="op">(</span><span class="op">-</span><span 