updated the pictures

Former-commit-id: e427c8181c

examples/01_prepare_data/data_prepare_retail.ipynb

@@ -160,11 +160,7 @@
     "\n",
     "Splitting time series data into a single round of trainig and testing data:\n",
     "![Single split](../../assets/time_series_split_singleround.jpg)\n",
-    "\n",
+    "\n"
-    "\n",
-    "\n",
-    "Splitting time series data into a multi round of trainig and testing data (for cross-validation):\n",
-    "![Multi split](../../assets/time_series_split_multiround.jpg)"
    ]
   },
   {
@@ -1112,6 +1108,12 @@
     "We can also create training data and test data for multi-round forecasting. In this case, we gradually increase the length of the training data at each round. Note that the forecasting period we generate in each round are non-overlapping. This allows us to retrain the forecasting model for achieving more accurate forecasts. Using the settings defined in the **Parameters** section above, and updating `N_SPLITS` to `10`, we can generate the training and test sets as follows:\n",
     "\n",
     "\n",
+    "\n",
+    "\n",
+    "Splitting time series data into a multi round of trainig and testing data (for cross-validation):\n",
+    "![Multi split](../../assets/time_series_split_multiround.jpg)\n",
+    "\n",
+    "\n",
     "| **Round** | **Train period <br> start week** | **Train period <br> end week** | **Test period <br> start week** | **Test period <br> end week** |\n",
     "| -------- | --------------- | ------------------ | ------------------------- | ----------------------- |\n",
     "| 1 | 40 | 135 | 137 | 138 |\n",