refactor how-to-guide

Author: janfb

docs/how_to_guide/19_posterior_parameters.ipynb

@@ -63,7 +63,7 @@
     "\n",
     "inference = NRE(prior=prior)\n",
     "inference.append_simulations(theta, x)\n",
-    "inference.train()"
+    "inference.train();"
    ]
   },
   {
@@ -81,7 +81,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from sbi.inference.posteriors.posterior_parameters import MCMCPosteriorParameters\n",
+    "from sbi.inference.posteriors import MCMCPosteriorParameters\n",
     "\n",
     "params = MCMCPosteriorParameters(\n",
     "    method=\"slice_np_vectorized\",\n",