What is an exotic function signature in Python?
<p>I recently saw a <a href="http://pypi.python.org/pypi/decorator/" rel="nofollow">reference to "exotic signatures"</a> and the fact they had been deprecated in 2.6 (and removed in 3.0). The example given is</p>

<pre><code>def exotic_signature((x, y)=(1,2)): return x+y
</code></pre>

<p>What makes this an "exotic" signature?</p>
