Expression Language - How can I determine if the User is a Proxy?

Summary:

How do I determine if the User logged-in is a Proxy, so I can disable

Content (required):

If the User is a Proxy, I'd like to disable certain menus/navigations or fields. For example, in OSC, if a user is logged as a Proxy, I'd like to disable the "About Me" on the Home Page Navigator. This is what I am doing:

1. In the Structure of the "About Me" page, I select "EL Expression" to the "Show on Navigator". In the Expression Editor, I have the following: #{fndGlobal.isImpersonating()}
2. When I validate, it returns True, I am logged-in as myself, and the "About Me" page is displayed in the Home Page Navigator