diff --git a/examples/positional_plotting.py b/examples/positional_plotting.py
index 4b4e6e0..171a3ba 100644
--- a/examples/positional_plotting.py
+++ b/examples/positional_plotting.py
@@ -7,26 +7,26 @@
 from oemof.network.energy_system import EnergySystem
 import oemof.network.graph as on_graph
 
-matplotlib.use('Qt5Agg')
+matplotlib.use("Qt5Agg")
 
-date_time_index = pd.date_range('1/1/2017', periods=3, freq='H')
+date_time_index = pd.date_range("1/1/2017", periods=3, freq="H")
 es = EnergySystem(timeindex=date_time_index)
-b_gas = Bus(label='b_gas', balanced=False)
-bel1 = Bus(label='bel1')
-bel2 = Bus(label='bel2')
-demand_el = Sink(label='demand_el', inputs=[bel1])
-pp_gas = Transformer(label=('pp', 'gas'),
-                     inputs=[b_gas],
-                     outputs=[bel1],
-                     conversion_factors={bel1: 0.5})
-line_to2 = Transformer(label='line_to2',
-                       inputs=[bel1],
-                       outputs=[bel2],
-                       position=(0, -3))
-line_from2 = Transformer(label='line_from2',
-                         inputs=[bel2],
-                         outputs=[bel1],
-                         position=(0, 3))
+b_gas = Bus(label="b_gas", balanced=False)
+bel1 = Bus(label="bel1")
+bel2 = Bus(label="bel2")
+demand_el = Sink(label="demand_el", inputs=[bel1])
+pp_gas = Transformer(
+    label=("pp", "gas"),
+    inputs=[b_gas],
+    outputs=[bel1],
+    conversion_factors={bel1: 0.5},
+)
+line_to2 = Transformer(
+    label="line_to2", inputs=[bel1], outputs=[bel2], position=(0, -3)
+)
+line_from2 = Transformer(
+    label="line_from2", inputs=[bel2], outputs=[bel1], position=(0, 3)
+)
 es.add(b_gas, bel1, demand_el, pp_gas, bel2, line_to2, line_from2)
 my_graph = on_graph.create_nx_graph(es)
 positions = on_graph.positions(es, my_graph)