Examples should use numpyro only if installed

[ricardoV94]

When you install pymc-marketing numpyro is not a requirement, but in several examples it's used.

I suggest having a pymc_marketing._numpyro_if_available variable (name up to discussion) that is "numpyro" if it's installed and "pymc" if not. Then the examples where we may want numpyro would have nuts_sample=_numpyro_if_available, and work.

In #1357 I actually changed one of the NBs to have a try/except but that clutters NBs a bit too much?

[wd60622]

Not a fan on the hidden name and that it is only for numpyro

What about a small class which checks the imports:

# pymc_marketing/utils.py
class InstalledSamplers(BaseModel): 
    nutpie: bool
    numpyro: bool 
    blackjax: bool

    @classmethod 
    def check(cls) -> InstalledSamplers: 
       # Check for all the requirements
    

installed_samplers = InstalledSamplers.check()

Then in notebook:

from pymc_marketing.utils import installed_samplers


model.fit(..., sampler="numpyro" if installed_samplers.numpyro else "pymc")

If user does inspect that object, it would have a nice repr

InstalledSamplers(nutpie=True, numpyro=False, blackjax=True)

[ricardoV94]

Sounds good