diff --git a/demos/getting_started_density.py b/demos/getting_started_density.py
index 62921ead7690670a146579c6b36ceeedf4a4583b..4a5c86a93a572e4af47d617d990e4da6c4e5fa2a 100644
--- a/demos/getting_started_density.py
+++ b/demos/getting_started_density.py
@@ -32,8 +32,8 @@ import nifty7 as ift
 
 
 def density_estimator(
-        domain, pad=1., cf_fluctuations=None, cf_azm_uniform=None
-    ):
+    domain, pad=1., cf_fluctuations=None, cf_azm_uniform=None
+):
     cf_azm_uniform_sane_default = (0., 20.)
     cf_fluctuations_sane_default = {
         "scale": (0.5, 0.3),
@@ -57,13 +57,12 @@ def density_estimator(
             )
             raise TypeError(te)
         shape_padded = tuple((d_scl * np.array(d.shape)).astype(int))
-        domain_padded.append(
-            ift.RGSpace(shape_padded, distances=d.distances)
-        )
+        domain_padded.append(ift.RGSpace(shape_padded, distances=d.distances))
     domain_padded = ift.DomainTuple.make(domain_padded)
 
     # Set up the signal model
-    prefix = "de"  # density estimator
+    prefix = "de_"  # density estimator
+    azm_offset_mean = 0.  # The zero-mode should be inferred only from the data
     cfmaker = ift.CorrelatedFieldMaker(prefix)
     for i, d in enumerate(domain_padded):
         if isinstance(cf_fluctuations, (list, tuple)):
@@ -74,7 +73,6 @@ def density_estimator(
     scalar_domain = ift.DomainTuple.scalar_domain()
     uniform = ift.UniformOperator(scalar_domain, *cf_azm_uni)
     azm = uniform.ducktape("zeromode")
-    azm_offset_mean = 0.  # The zero-mode should be inferred only from the data
     cfmaker.set_amplitude_total_offset(azm_offset_mean, azm)
     correlated_field = cfmaker.finalize(0)
     normalized_amplitudes = cfmaker.get_normalized_amplitudes()
@@ -109,21 +107,25 @@ if __name__ == "__main__":
     rng = ift.random.current_rng()
     rng.standard_normal(1000)
     mock_position = ift.from_random(signal.domain, 'normal')
-    data = ift.Field.from_raw(data_space, rng.poisson(signal(mock_position).val))
+    data = ift.Field.from_raw(
+        data_space, rng.poisson(signal(mock_position).val)
+    )
 
     plot = ift.Plot()
-    plot.add(ift.exp(correlated_field(mock_position)), title='Pre-Slicing Truth')
+    plot.add(
+        ift.exp(correlated_field(mock_position)), title='Pre-Slicing Truth'
+    )
     plot.add(signal(mock_position), title='Ground Truth')
     plot.add(data, title='Data')
     plot.output(ny=1, nx=3, xsize=10, ysize=10, name=filename.format("setup"))
 
     # Minimization parameters
-    ic_sampling = ift.AbsDeltaEnergyController(name='Sampling',
-                                               deltaE=0.01,
-                                               iteration_limit=100)
-    ic_newton = ift.AbsDeltaEnergyController(name='Newton',
-                                             deltaE=0.01,
-                                             iteration_limit=35)
+    ic_sampling = ift.AbsDeltaEnergyController(
+        name='Sampling', deltaE=0.01, iteration_limit=100
+    )
+    ic_newton = ift.AbsDeltaEnergyController(
+        name='Newton', deltaE=0.01, iteration_limit=35
+    )
     ic_sampling.enable_logging()
     ic_newton.enable_logging()
     minimizer = ift.NewtonCG(ic_newton, enable_logging=True)
@@ -150,16 +152,23 @@ if __name__ == "__main__":
         plot.add(ift.exp(correlated_field(mock_position)), title="ground truth")
         plot.add(signal(mock_position), title="ground truth")
         plot.add(signal(kl.position), title="reconstruction")
-        plot.add((ic_newton.history, ic_sampling.history,
-                  minimizer.inversion_history),
-                 label=['kl', 'Sampling', 'Newton inversion'],
-                 title='Cumulative energies', s=[None, None, 1],
-                 alpha=[None, 0.2, None])
-        plot.output(nx=3,
-                    ny=2,
-                    ysize=10,
-                    xsize=15,
-                    name=filename.format(f"loop_{i:02d}"))
+        plot.add(
+            (
+                ic_newton.history, ic_sampling.history,
+                minimizer.inversion_history
+            ),
+            label=['kl', 'Sampling', 'Newton inversion'],
+            title='Cumulative energies',
+            s=[None, None, 1],
+            alpha=[None, 0.2, None]
+        )
+        plot.output(
+            nx=3,
+            ny=2,
+            ysize=10,
+            xsize=15,
+            name=filename.format(f"loop_{i:02d}")
+        )
 
     # Done, draw posterior samples
     sc = ift.StatCalculator()
@@ -174,7 +183,10 @@ if __name__ == "__main__":
     plot.add(sc.mean, title="Posterior Mean")
     plot.add(ift.sqrt(sc.var), title="Posterior Standard Deviation")
     plot.add(sc_unsliced.mean, title="Posterior Unsliced Mean")
-    plot.add(ift.sqrt(sc_unsliced.var), title="Posterior Unsliced Standard Deviation")
+    plot.add(
+        ift.sqrt(sc_unsliced.var),
+        title="Posterior Unsliced Standard Deviation"
+    )
 
     plot.output(ny=2, nx=2, xsize=15, ysize=15, name=filename_res)
     print("Saved results as '{}'.".format(filename_res))