title: Using "if" as argument identifier
body: <p>I want to generate the following xml file:</p>
  
  <pre><code>&lt;foo if="bar"/&gt;
  </code></pre>
  
  <p>I've tried this:</p>
  
  <pre><code>from lxml import etree
  etree.Element("foo", if="bar")
  </code></pre>
  
  <p>But I got this error:</p>
  
  <pre><code>page = etree.Element("configuration", if="ok")
                                         ^
  SyntaxError: invalid syntax
  </code></pre>
  
  <p>Any ideas?</p>
  
  <p>I'm using python 2.7.9 and lxml 3.4.2</p>