revise part 1 and part 2

Author: mingyu-yuan

lessons/01_python_data_visualization.ipynb

@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Python Data Visualization\n",
+    "# Python Data Visualization: Part 1\n",
     "\n",
     "* * * \n",
     "\n",
@@ -658,7 +658,7 @@
    "source": [
     "Syntax: call the **dataframe** (`gm_latest`), followed by the plot type (`.hist()`): `gm_latest.hist()`\n",
     "\n",
-    "Let's check out the [documentation](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.hist.html) of `pd.hist()`. The required input values is a column of a dataframe. We no longer need to select the column using square brackets, but simplying passing in the name of the column to the parameter `column`. Now you can see how `pandas` differs from `matplotlib`. The function `pd.hist()` is not meant to be a generic plotting method; it is rather specific to the dataframe where the data comes from. "
+    "Let's check out the [documentation](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.hist.html) of `pd.hist()`. The required input value is a column of a dataframe. We no longer need to select the column using square brackets, but simplying passing in the name of the column to the parameter `column`. Now you can see how `pandas` differs from `matplotlib`. The function `pd.hist()` is not meant to be a generic plotting method; it is rather specific to the dataframe where the data comes from. "
    ]
   },
   {

lessons/02_python_data_visualization.ipynb

@@ -25,11 +25,11 @@
     "🎬 **Demo**: Showing off something more advanced – so you know what Python can be used for!<br> \n",
     "\n",
     "### Sections\n",
-    "6. [Scatter Plot](#section6)\n",
-    "7. [Line Plot](#section7)\n",
-    "8. [Subplot](#section8)\n",
-    "9. [Customization](#section9)\n",
-    "7. [Demo: Change Plot Styles](#section10)"
+    "7. [Scatter Plot](#section6)\n",
+    "8. [Line Plot](#section7)\n",
+    "9. [Subplot](#section8)\n",
+    "10. [Customization](#section9)\n",
+    "11. [Demo: Change Plot Styles](#section10)"
    ]
   },
   {