[Feature]: Add priori of equation form

[zhuyi-bjut]

Feature Request

Hi！When I want to find some expressions from my data, I want his form to be specific. For example, I hope that the equation form obtained by pysr is C1 * x1 + ( C2 * x2 / F ), where F is the term to be found, C1 and C2 are constants to be found. This is equivalent to the form of a constrained expression tree, that is, adding a priori. Is it possible for today 's pysr to implement this function ?
Thanks！

[MilesCranmer]

Hi @prozhuyi,

The current method for doing this is exemplified here: https://astroautomata.com/PySR/examples/#9-custom-objectives. An easier way to do this is being discussed here: MilesCranmer/SymbolicRegression.jl#193. (Help is always appreciated!)

Cheers,
Miles