def pop_fbo(self):
        """ Pop an FBO from the stack.
        """
        fbo = self._fb_stack.pop()
        fbo[0].deactivate()
        self.pop_viewport()
        if len(self._fb_stack) > 0:
            old_fbo = self._fb_stack[-1]
            old_fbo[0].activate()
        
        self._update_transforms()
        return fbo
Pop an FBO from the stack.