What does self[] mean in a method?
<p>When reading a python program, I once find a function uses <code>self</code> in the following way. </p>

<pre><code>class Auto(object):
   _biases_str = "biases{0}"

   def _b(self, n, suffix=""):
     name_b_out = self._biases_str.format(i + 1) + "_out"
     return `self[self._biases_str.format(n) + suffix]`
</code></pre>

<p>The line of <code>name_b_out = self._biases_str.format(i + 1) + "_out"</code>  looks usual to me, i.e., we always <code>self.</code> to define something. But I am not very clear about the usage of <code>self[self._biases_str.format(n) + suffix]</code>. In specifc, what does <code>self[]</code> mean here, or what does it do?</p>