Fix for figures in the Granger causality tutorial (NeuralEnsemble#434)

The plots generated in the Granger causality tutorial had incorrect axis ranges. This was fixed by setting x- and y-axis bounds in both plots.

- Fixed the figures in granger_causality.ipynb tutorial

doc/tutorials/granger_causality.ipynb

@@ -51,6 +51,8 @@
     "ax1.text(0.5, 0.6, 'Z', horizontalalignment='center', verticalalignment='center')\n",
     "ax1.text(0.8, 0.2, 'X', horizontalalignment='center', verticalalignment='center')\n",
     "ax1.set_title('Indirect only')\n",
+    "ax1.set_xbound((0, 1))\n",
+    "ax1.set_ybound((0, 0.8))\n",
     "\n",
     "ax1.tick_params(axis='both', which='both', bottom=False, top=False, labelbottom=False, \n",
     "                right=False, left=False, labelleft=False)\n",
@@ -69,11 +71,13 @@
     "ax2.text(0.2, 0.2, 'Y', horizontalalignment='center', verticalalignment='center')\n",
     "ax2.text(0.5, 0.6, 'Z', horizontalalignment='center', verticalalignment='center')\n",
     "ax2.text(0.8, 0.2, 'X', horizontalalignment='center', verticalalignment='center')\n",
+    "ax2.set_xbound((0, 1))\n",
+    "ax2.set_ybound((0, 0.8))\n",
     "\n",
     "ax2.tick_params(axis='both', which='both', bottom=False, top=False, labelbottom=False, \n",
     "                right=False, left=False, labelleft=False)\n",
     "ax2.set_title('Both direct and indirect')\n",
-    "\n",
+    "plt.tight_layout()\n",
     "plt.show()"
    ]
   },
@@ -223,7 +227,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.5"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,