code: def pop_fbo(self):
          
          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
docs: Pop an FBO from the stack.