merged dmatrix branch that uses dmatrix to initialize each model.

give a str and a dict to initialize.

pyPLNmodels/__init__.py

 from .models import PLNPCA, PLN  # pylint:disable=[C0114]
 from .elbos import profiled_elbo_pln, elbo_plnpca, elbo_pln
-from ._utils import get_simulated_count_data, get_real_count_data
+from ._utils import (
+    get_simulated_count_data,
+    get_real_count_data,
+    load_model,
+    load_plnpca,
+    load_pln,
+)
 
 __all__ = (
     "PLNPCA",
@@ -10,4 +16,7 @@ __all__ = (
     "elbo_pln",
     "get_simulated_count_data",
     "get_real_count_data",
+    "load_model",
+    "load_plnpca",
+    "load_pln",
 )