remove deprecation warning related to pm.sample returning idata (#295)

* remove deprecation warning related to pm.sample returning idata

* pylint

bambi/backends/pymc.py

@@ -1,7 +1,6 @@
 import logging
 
 import numpy as np
-from arviz import from_pymc3
 import theano
 import pymc3 as pm
 
@@ -123,7 +122,7 @@ def run(
             The method to use for fitting the model. By default, 'mcmc', in which case the
             PyMC3 sampler will be used. Alternatively, 'advi', in which case the model will be
             fitted using  automatic differentiation variational inference as implemented in PyMC3.
-            Finally, 'laplace', in wich case a laplace approximation is used, 'laplace' is not
+            Finally, 'laplace', in which case a laplace approximation is used, 'laplace' is not
             recommended other than for pedagogical use.
         init: str
             Initialization method (see PyMC3 sampler documentation). Currently, this is
@@ -145,9 +144,14 @@ def run(
         if method.lower() == "mcmc":
             draws = kwargs.pop("draws", 1000)
             with model:
-                self.trace = pm.sample(draws, start=start, init=init, n_init=n_init, **kwargs)
-
-            idata = from_pymc3(self.trace, model=model)
+                idata = pm.sample(
+                    draws,
+                    start=start,
+                    init=init,
+                    n_init=n_init,
+                    return_inferencedata=True,
+                    **kwargs,
+                )
 
             if omit_offsets:
                 offset_dims = [vn for vn in idata.posterior.dims if "offset" in vn]