How do I set up a basis function consisting of three different inputs x, y, z?

[Shota123-pixel]

Feature Request

I would like to set up a basis function consisting of three different inputs x, y, z.
For example, what should we do when we want to set up the following basis functions?

function basis_1
return x + y + 2*z

I have been able to define a basis function with two variables using the binary_operators option, but I am having trouble setting up a basis function with three variables.
If you have any suggestions on how to do this, I'd appreciate it if you could let me know.

[MilesCranmer]

Hi @Shota123-pixel,

3-input operators are not yet allowed, but this is on the roadmap. I would recommend splitting the operator into two 2-input operators, like x + y and x + 2*y for your example, which would be composed to x + y + 2*z.

Cheers,
Miles

[Shota123-pixel]

Thank you very much for your kind answer!
I will try your recommendation!