How to obtain tensor expression of fixed form equation by pysr?

[ccclalala123]

Hi!
I want to use pysr to train the expressions $f_{1}$, $f_{2}$, $f_{3}$ in the following fluid mechanics tensor equations：
$\tau_{\mathrm{ij}}=\frac{1-f_1(I_{1_{ij}},I_{2_{ij}})}3\times T_{1_{ij}}+\frac{f_2(I_{2_{ij}},I_{3_{ij}})}6\times T_{2_{ij}}+\frac{1-f_3(I_{3_{ij}},I_{4_{ij}})}3\times T_{3_{ij}}$
where the subscrip i=1,2,3; j=1,2,3; $\tau,I_1,I_2,I_3,I_4,T_1,T_2,T_3$ are all in the form of a 3×3 tensor matrix.
How do I get $f_{1}$(expressions about $I_{1_{ij}}$ and $I_{2_{ij}}$) , $f_{2}$ (expressions about $I_{2_{ij}}$ and $I_{3_{ij}}$) , $f_{3}$ (expressions about $I_{3_{ij}}$ and $I_{4_{ij}}$) from pysr?
Much appreciated!

[MilesCranmer]

Hi, can you please provide more info about what you've tried and what issues you are facing? Thanks