diff --git a/.docker/Dockerfile b/.docker/Dockerfile
index 43e5eff1171da8d69eb8897bea678bf90572570a..7fa7fc1e3ba287611b84d22cd969ef50655f8a8f 100644
--- a/.docker/Dockerfile
+++ b/.docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM debian:10
+FROM debian:11
 RUN apt-get update && \
     apt-get install \
     curl \
@@ -13,7 +13,7 @@ RUN apt-get update && \
     tox \
     git \
     openjdk-11-jdk-headless \
-    python-autopep8 \
+    python3-autopep8 \
     python3-pytest \
     libxml2 \
     -y
diff --git a/src/caosadvancedtools/models/data_model.py b/src/caosadvancedtools/models/data_model.py
index a4804dd0fb0300af9b166717f41f341a57b677d4..e198d15ca2c56eceec29c356cabdf28ac44895b2 100644
--- a/src/caosadvancedtools/models/data_model.py
+++ b/src/caosadvancedtools/models/data_model.py
@@ -23,6 +23,11 @@
 # ** end header
 #
 from copy import deepcopy
+# TODO(fspreck) for backwards compatibility with Python < 3.9 but this is
+# actually
+# [deprecated](https://docs.python.org/3/library/typing.html#typing.List), so
+# remove this, when we drop support for old Python versions.
+from typing import List
 
 import caosdb as db
 from caosdb.apiutils import compare_entities, describe_diff
@@ -68,14 +73,14 @@ class DataModel(dict):
         else:
             super().__init__(args)
 
-    def append(self, entity):
+    def append(self, entity: db.Entity):
         self[entity.name] = entity
 
-    def extend(self, entities):
+    def extend(self, entities: List[db.Entity]):
         for entity in entities:
             self.append(entity)
 
-    def sync_data_model(self, noquestion=False):
+    def sync_data_model(self, noquestion: bool = False, verbose: bool = True):
         """Synchronize this DataModel with a CaosDB instance.
 
         Updates existing entities from the CaosDB instance and inserts
@@ -100,23 +105,27 @@ class DataModel(dict):
         self.sync_ids_by_name(tmp_exist)
 
         if len(non_existing_entities) > 0:
-            print("New entities:")
+            if verbose:
+                print("New entities:")
 
-            for ent in non_existing_entities:
-                print(ent.name)
+                for ent in non_existing_entities:
+                    print(ent.name)
 
             if noquestion or str(input("Do you really want to insert those "
                                        "entities? [y/N] ")).lower() == "y":
                 non_existing_entities.insert()
                 self.sync_ids_by_name(non_existing_entities)
-                print("Updated entities.")
+                if verbose:
+                    print("Updated entities.")
             else:
                 return
         else:
-            print("No new entities.")
+            if verbose:
+                print("No new entities.")
 
         if len(existing_entities) > 0:
-            print("Inspecting changes that will be made...")
+            if verbose:
+                print("Inspecting changes that will be made...")
             any_change = False
 
             for ent in existing_entities:
@@ -126,18 +135,22 @@ class DataModel(dict):
                                                         ), name=ent.name))
 
                 if diff != "":
-                    print(diff)
+                    if verbose:
+                        print(diff)
                     any_change = True
 
             if any_change:
                 if noquestion or input("Do you really want to apply the above "
                                        "changes? [y/N]") == "y":
                     existing_entities.update()
-                    print("Synchronized existing entities.")
+                    if verbose:
+                        print("Synchronized existing entities.")
             else:
-                print("No differences found. No update")
+                if verbose:
+                    print("No differences found. No update")
         else:
-            print("No existing entities updated.")
+            if verbose:
+                print("No existing entities updated.")
 
     @staticmethod
     def get_existing_entities(entities):