From OpenGL to glium: Chain of framebuffers

Trying to figure out how I can do something similar to this (C++ code) using glium What it does is configure a 'pipeline' of image transformations from framebuffer to framebuffer. Notice the bottom-most function. Lines 90-98 connect two framebuffers.

I guess I'll use SimpleFrameBuffers. But I'll need to use the texture/RendeObject of one FrameBuffer as the input of a shader program... that is, I need to set the sampler2D uniform of the shader program to the SimpleFrameBuffer's texture. How can I obtain this texture?