title: In Clojure why use :only []
body: <p>The source for <a href="https://github.com/richhickey/clojure-contrib/blob/bbe248f90e6ec33d5e85d2267fa1caf8c7cb99a7/src/main/clojure/clojure/contrib/lazy_xml.clj#L15" rel="noreferrer">lazy-xml</a> has the following:</p>
  
  <pre><code>(:use [clojure.xml :as xml :only []]
        [clojure.contrib.seq :only [fill-queue]])
  </code></pre>
  
  <p>What is the purpose of using <code>clojure.xml</code> but listing nothing for the <code>:only</code> arguments?</p>