Fix early stopping example, fixes ageron#190

Author: ageron

04_training_linear_models.ipynb

@@ -1340,7 +1340,7 @@
    },
    "outputs": [],
    "source": [
-    "from sklearn.base import clone\n",
+    "from copy import deepcopy\n",
     "\n",
     "poly_scaler = Pipeline([\n",
     "        (\"poly_features\", PolynomialFeatures(degree=90, include_bias=False)),\n",
@@ -1363,8 +1363,7 @@
     "    if val_error < minimum_val_error:\n",
     "        minimum_val_error = val_error\n",
     "        best_epoch = epoch\n",
-    "        best_model = sgd_reg\n",
-    "        sgd_reg = clone(sgd_reg)"
+    "        best_model = deepcopy(sgd_reg)"
    ]
   },
   {