add import pytest in docs_and_testing notebook

Author: gantian127

lessons/python/docs_and_testing.ipynb

@@ -218,6 +218,16 @@
     "Pytest supports parameterization, which allows a single unit test function to run multiple scenarios with different input values. The pytest.mark.parametrize is a decorator provided by pytest, which allows you to run the same test function multiple times with different sets of arguments. Below is an example using parameterization to test the case for invalid degree_day_factor. The pytest.raises context manager is used when we expect an exception to be raised during function execution—such as a ValueError for invalid inputs."
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c1989288-17f6-4a0a-843e-77f4a7fd018e",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import pytest"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,