Fixed jupyter not working

src/1_einstein_model_solutions.md

+---
+jupyter:
+  jupytext:
+    text_representation:
+      extension: .md
+      format_name: markdown
+      format_version: '1.0'
+      jupytext_version: 0.8.6
+  kernelspec:
+    display_name: Python 3
+    language: python
+    name: python3
+---
+
+```python tags=["initialize"]
+from matplotlib import pyplot as plt
+from mpl_toolkits.axes_grid1 import make_axes_locatable
+
+import numpy as np
+from scipy.optimize import curve_fit
+from scipy.integrate import quad
+
+from common import draw_classic_axes, configure_plotting
+
+configure_plotting()
+```
+
 # Solutions for lecture 1 exercises
 ### Warm-up exercises
 1. An ideal gas only contains 3 positional degrees of freedom.
 2. $C = 2k_B$.
 3. See image below
 ```python
-import matplotlib.pyplot as plt
-import numpy as np
-
 fig, ax = plt.subplots()
 omega = np.linspace(0.1, 3)
 T = [1,2]