public static SecurityManager unbindSecurityManager() {
        return (SecurityManager) remove(SECURITY_MANAGER_KEY);
    }
Convenience method that simplifies removal of the application's SecurityManager instance from the thread.
<p/>
The implementation just helps reduce casting and remembering of the ThreadContext key name, i.e it is
merely a convenient wrapper for the following:
<p/>
<code>return (SecurityManager)remove( SECURITY_MANAGER_KEY );</code>
<p/>
If you wish to just retrieve the object from the thread without removing it (so it can be retrieved later
during thread execution), use the {@link #getSecurityManager() getSecurityManager()} method instead.

@return the application's SecurityManager instance previously bound to the thread, or <tt>null</tt> if there
was none bound.
@since 0.9
core/src/main/java/org/apache/shiro/util/ThreadContext.java