diff --git a/moler/device/pdu_aten3.py b/moler/device/pdu_aten3.py
index 8025be87b..a60a149bb 100644
--- a/moler/device/pdu_aten3.py
+++ b/moler/device/pdu_aten3.py
@@ -76,8 +76,8 @@ def __init__(self, sm_params, name=None, io_connection=None, io_type=None, varia
         sm_params = sm_params.copy()
         initial_state = initial_state if initial_state is not None else PduAten3.pdu
         super(PduAten3, self).__init__(sm_params=sm_params, name=name, io_connection=io_connection,
-                                      io_type=io_type, variant=variant, io_constructor_kwargs=io_constructor_kwargs,
-                                      initial_state=initial_state, lazy_cmds_events=lazy_cmds_events)
+                                       io_type=io_type, variant=variant, io_constructor_kwargs=io_constructor_kwargs,
+                                       initial_state=initial_state, lazy_cmds_events=lazy_cmds_events)
         self.logger = logging.getLogger('moler.pdu')
 
     @mark_to_call_base_class_method_with_same_name
diff --git a/moler/device/scpi3.py b/moler/device/scpi3.py
index 0933780c7..145e4a4a3 100644
--- a/moler/device/scpi3.py
+++ b/moler/device/scpi3.py
@@ -80,8 +80,8 @@ def __init__(self, sm_params, name=None, io_connection=None, io_type=None, varia
         sm_params = sm_params.copy()
         initial_state = initial_state if initial_state is not None else Scpi3.scpi
         super(Scpi3, self).__init__(sm_params=sm_params, name=name, io_connection=io_connection, io_type=io_type,
-                                   variant=variant, io_constructor_kwargs=io_constructor_kwargs,
-                                   initial_state=initial_state, lazy_cmds_events=lazy_cmds_events)
+                                    variant=variant, io_constructor_kwargs=io_constructor_kwargs,
+                                    initial_state=initial_state, lazy_cmds_events=lazy_cmds_events)
         self.logger = logging.getLogger('moler.scpi')
 
     @mark_to_call_base_class_method_with_same_name
diff --git a/moler/helpers.py b/moler/helpers.py
index e23a5ebac..d0546d529 100644
--- a/moler/helpers.py
+++ b/moler/helpers.py
@@ -638,12 +638,19 @@ def _delete_state(sm: dict, state_to_remove: str) -> None:
         if from_state in sm and state_to_remove in sm[from_state]:
             del sm[from_state][state_to_remove]
 
+
 def _delete_empty_states(sm: dict) -> None:
+    """
+    Delete empty states from a state machine dict (in place).
+    :param sm: dict with state machine
+    :return: None
+    """
     states = list(sm.keys())
     for state in states:
         if sm[state] is None or not sm[state]:
             del sm[state]
 
+
 def remove_state_hops_from_sm(source_hops: dict, state_to_remove: str) -> dict:
     """
     Remove a state from a state machine dict.