[Zope] TAL - authentication

[Tom Nixon]

I want to have a <span> with a tal:condition clause that means it's only
displayed if there is an authenticated user logged in, or alternatively
if the user has particular privileges. In DTML it would be something
like the following but I'm not sure about how to do it in TAL.

<dtml-if expr="_.SecurityCheckPermission('Add Documents, Images, and
Files', this())">
 Hello authorised user
</dtml-if>

I assume something like this:
<span tal:condition="python:someSecurityFunction()"
tal:replace="string:Hello authorised user"></span>

T.