Linking texture functions in "direct_call" mode for Optix7

I’m a bit confused by two examples in the SDK; execution_cuda and optix7. In the first one, in direct call mode, it shows how to compile the module to link the texture functions like tex_lookup_float4_2d that maps to tex::lookup_float4(). But the compilation is directly into a cuda module (cubin file).

But, in Optix7, you must provide PTX code that is ompiled and then used to create callables that can be added in the binding table.

What confuses me is with Optix7, how can I merge a PTX, from an MDL, with the texture functions that I would implement (already compiled to PTX).