patsy equivalent of R's all.vars

[Xiaojieqiu]

Hey patsy developers, I wonder how can we retrieve the variable names from the model formula string (in R, this can be done via the all.vars function). For example,

if I have ("y ~ x1:x2 + np.log(x3) + I(x4^2)"), I want to return a list of ['x1', 'x2', 'x3', 'x4'].
Similarly, if I have ("~cr(time, df = 3)"), I want to return a list of ['time'].

Your help is highly appreciated!

[compumetrika]

I noticed your issue when I was writing up my own. I posted a solution to a different but related problem here; you may be able to use this to solve your problem: #171

It isn't an implementation of all.vars but may none the less still be useful.
Good luck!