title: Python dunder method for `is`
body: <p>While looking through the docs, and specifically here <a href="http://docs.python.org/2/reference/expressions.html#is" rel="noreferrer">http://docs.python.org/2/reference/expressions.html#is</a>, I still can't find the dunder/protocol method that defines the implementation of the Python keyword <code>is</code>. What method determines it? From what I understand, all <code>is</code> does is to compare the results of the <code>id</code> function when called on two objects.</p>