title: Signature method in Inspect module for python 2
body: <p>I am trying to run a Python 3 library in Python 2. It uses <code>inspect</code> module and <code>signature</code> method which is not implemented in Python 2 version of the module.</p>
  
  <pre><code>signature = inspect.signature(initializer)
  </code></pre>
  
  <p>There is no implementation in <code>__future__</code> that can help (at least, I haven't found one).</p>
  
  <p>How can I replace this method?</p>