Again, chained comparisons. For any comparison operator (comparison operators are &lt;, &gt;, ==, &gt;=, &lt;=, &lt;&gt;, !=, &#x27;is&#x27;, &#x27;not&#x27;, &#x27;is not&#x27;, &#x27;in&#x27; and &#x27;not in&#x27;):<p><pre><code>    x (operator1) y (operator2) z
</code></pre>
is defined by the language as equivalent to<p><pre><code>    (x (operator1) y) and (y (operator2) z)
</code></pre>
So<p><pre><code>    1 in [1] in [[1]]
</code></pre>
is equivalent to<p><pre><code>    (1 in [1]) and ([1] in [[1]])
</code></pre>
For any comparison operator