diff --git a/sktime/transformations/series/compose.py b/sktime/transformations/series/compose.py
index 5de938ad3bc..c0302c020cb 100644
--- a/sktime/transformations/series/compose.py
+++ b/sktime/transformations/series/compose.py
@@ -3,11 +3,6 @@
 # copyright: sktime developers, BSD-3-Clause License (see LICENSE file)
 """Meta-transformers for building composite transformers."""
 
-"""Series-to-Series Transformers: OptionalPassthrough and Columnwisetransformer."""
-
-__author__ = ["Martin Walter", "Svea Meyer"]
-__all__ = ["OptionalPassthrough", "ColumnwiseTransformer"]
-
 import pandas as pd
 from sktime.transformations.base import _SeriesToSeriesTransformer
 from sktime.utils.validation.series import check_series
@@ -15,6 +10,9 @@
 from sklearn.base import clone
 from sklearn.utils.metaestimators import if_delegate_has_method
 
+__author__ = ["Martin Walter", "Svea Meyer"]
+__all__ = ["OptionalPassthrough", "ColumnwiseTransformer"]
+
 
 class OptionalPassthrough(_SeriesToSeriesTransformer):
     """Wrap an existing transformer to tune whether to include it in a pipeline.
@@ -32,7 +30,6 @@ class OptionalPassthrough(_SeriesToSeriesTransformer):
         This arg decides whether to apply the given transformer or to just
         passthrough the data (identity transformation)
 
-
     Examples
     --------
     >>> from sktime.datasets import load_airline
@@ -83,7 +80,7 @@ def __init__(self, transformer, passthrough=False):
         super(OptionalPassthrough, self).__init__()
 
     def fit(self, Z, X=None):
-        """Fit the model."""
+        """Fit the model.
 
         Parameters
         ----------
@@ -103,7 +100,7 @@ def fit(self, Z, X=None):
         return self
 
     def transform(self, Z, X=None):
-        """Apply transformation."""
+        """Apply transformation.
 
         Parameters
         ----------