Automate code conversion between different ML framework

This is just a question, Currently, it is not possible to convert code directly between different ML frameworks, such as JAX and Pytorch. what do you think are the biggest challenges? and how can this be solved. just need peoples views on this.

I have come across ivy package which tries to achieve this.
I have not tried it yet.

i have come across it, i just want to know the technical problem one might face trying to achieve this.