Condition "if" in mixin in Jade
<p>I am looking for the way to use "if" in mixin.</p>

<pre><code>mixin fn(a)
    if a == "some"
        ...
    else
        ...

+fn("some")
</code></pre>

<p>Unfortunately, It doesn't work. And seems like "if" couldn't get the parameter "a". How could I deal with? </p>