diff --git a/doc/source/examples/notebooks/example_4.pct.py b/doc/source/examples/notebooks/example_4.pct.py
index 56bd6a00..7f875f56 100644
--- a/doc/source/examples/notebooks/example_4.pct.py
+++ b/doc/source/examples/notebooks/example_4.pct.py
@@ -1,7 +1,5 @@
 # %% [markdown]
-"""
-# Example 4: A loss assessment including both damage states and loss functions.
-"""
+"""# Example 4: A loss assessment including both damage states and loss functions."""
 
 # %%
 import tempfile
@@ -14,7 +12,6 @@
 from pelicun import assessment, file_io
 from pelicun.pelicun_warnings import PelicunWarning
 
-
 temp_dir = tempfile.mkdtemp()
 
 sample_size = 10000
@@ -77,8 +74,9 @@
 # Generate samples
 asmnt.demand.generate_sample({'SampleSize': sample_size})
 
+
 def add_more_edps() -> None:
-    """Adds SA_1.13 and residual drift to the demand sample."""
+    """Add SA_1.13 and residual drift to the demand sample."""
     # Add residual drift and Sa
     demand_sample = asmnt.demand.save_sample()
 
@@ -107,6 +105,7 @@ def add_more_edps() -> None:
 
     asmnt.demand.load_sample(demand_sample_ext)
 
+
 add_more_edps()
 
 #
@@ -117,9 +116,7 @@ def add_more_edps() -> None:
 asmnt.stories = 1
 
 # Load component definitions
-cmp_marginals = pd.read_csv(
-    'example_4/CMP_marginals.csv', index_col=0
-)
+cmp_marginals = pd.read_csv('example_4/CMP_marginals.csv', index_col=0)
 cmp_marginals['Blocks'] = cmp_marginals['Blocks']
 asmnt.asset.load_cmp_model({'marginals': cmp_marginals})
 
diff --git a/pelicun/model/damage_model.py b/pelicun/model/damage_model.py
index afeada00..8977df1d 100644
--- a/pelicun/model/damage_model.py
+++ b/pelicun/model/damage_model.py
@@ -1362,7 +1362,7 @@ def parse_scaling_specification(scaling_specification: dict) -> dict:  # noqa: C
             """
             # if there are contents, ensure they are valid.
             # See docstring for an example of what is expected.
-            parsed_scaling_specification = defaultdict(dict)
+            parsed_scaling_specification: dict = defaultdict(dict)
             # validate contents
             for key, value in scaling_specification.items():
                 # loop through limit states
diff --git a/pelicun/tests/basic/test_damage_model.py b/pelicun/tests/basic/test_damage_model.py
index eb079a15..51d57676 100644
--- a/pelicun/tests/basic/test_damage_model.py
+++ b/pelicun/tests/basic/test_damage_model.py
@@ -591,6 +591,8 @@ def test__create_dmg_RVs(self, assessment_instance: Assessment) -> None:
         for rv_name, rv in capacity_rv_reg.RV.items():
             uniform_sample = rv._uni_sample
             sample = rv.sample
+            assert uniform_sample is not None
+            assert sample is not None
             for i in range(len(operation_list)):
                 if rv_name == 'FRG-cmp.A-1-2-3-1-1':
                     theta = 1.20 * 30.0