k&lt;Response&gt; cb);
 </pre>
 <p>
 Header parameters may be <code>null</code> which will omit them from the request. Passing a
 <a href="http://java.sun.com/javase/6/docs/api/java/util/List.html?is-external=true" title="class or interface in java.util"><code>List</code></a> or array will result in a header for each non-<code>null</code> item.
 <p>
 <strong>Note:</strong> Headers do not overwrite each other. All headers with the same name will
 be included in the request.</div>
<dl>
<dt><span class="simple