diff --git a/airflow/decorators/base.py b/airflow/decorators/base.py
index 229a114fc9cfb..055712529f835 100644
--- a/airflow/decorators/base.py
+++ b/airflow/decorators/base.py
@@ -19,7 +19,7 @@
 import inspect
 import re
 from inspect import signature
-from typing import Any, Callable, Dict, Optional, Tuple, TypeVar, cast
+from typing import Any, Callable, Dict, Iterable, Optional, Tuple, Type, TypeVar, cast
 
 from airflow.exceptions import AirflowException
 from airflow.models import BaseOperator
@@ -101,7 +101,7 @@ class DecoratedOperator(BaseOperator):
     :type kwargs_to_upstream: dict
     """
 
-    template_fields = ('op_args', 'op_kwargs')
+    template_fields: Iterable[str] = ('op_args', 'op_kwargs')
     template_fields_renderers = {"op_args": "py", "op_kwargs": "py"}
 
     # since we won't mutate the arguments, we should just do the shallow copy
@@ -180,7 +180,7 @@ def _hook_apply_defaults(self, *args, **kwargs):
 def task_decorator_factory(
     python_callable: Optional[Callable] = None,
     multiple_outputs: Optional[bool] = None,
-    decorated_operator_class: BaseOperator = None,
+    decorated_operator_class: Type[BaseOperator] = None,
     **kwargs,
 ) -> Callable[[T], T]:
     """
diff --git a/airflow/providers/docker/decorators/docker.py b/airflow/providers/docker/decorators/docker.py
index 7421cda1cef9f..e1830ea7bd8d7 100644
--- a/airflow/providers/docker/decorators/docker.py
+++ b/airflow/providers/docker/decorators/docker.py
@@ -62,7 +62,7 @@ class _DockerDecoratedOperator(DecoratedOperator, DockerOperator):
     :type multiple_outputs: bool
     """
 
-    template_fields = ('op_args', 'op_kwargs')
+    template_fields: Iterable[str] = ('op_args', 'op_kwargs')
 
     # since we won't mutate the arguments, we should just do the shallow copy
     # there are some cases we can't deepcopy the objects (e.g protobuf).
diff --git a/airflow/providers/docker/hooks/docker.py b/airflow/providers/docker/hooks/docker.py
index 49c76c71ad1e8..76db2d84505d2 100644
--- a/airflow/providers/docker/hooks/docker.py
+++ b/airflow/providers/docker/hooks/docker.py
@@ -52,7 +52,7 @@ def get_ui_field_behaviour() -> Dict:
 
     def __init__(
         self,
-        docker_conn_id: str = default_conn_name,
+        docker_conn_id: Optional[str] = default_conn_name,
         base_url: Optional[str] = None,
         version: Optional[str] = None,
         tls: Optional[str] = None,
@@ -63,7 +63,11 @@ def __init__(
         if not version:
             raise AirflowException('No Docker API version provided')
 
+        if not docker_conn_id:
+            raise AirflowException('No Docker connection id provided')
+
         conn = self.get_connection(docker_conn_id)
+
         if not conn.host:
             raise AirflowException('No Docker URL provided')
         if not conn.login:
@@ -87,7 +91,7 @@ def get_conn(self) -> APIClient:
         self.__login(client)
         return client
 
-    def __login(self, client) -> int:
+    def __login(self, client) -> None:
         self.log.debug('Logging into Docker')
         try:
             client.login(
diff --git a/airflow/providers/docker/operators/docker.py b/airflow/providers/docker/operators/docker.py
index 506e89ae4d91f..652424fac4aa5 100644
--- a/airflow/providers/docker/operators/docker.py
+++ b/airflow/providers/docker/operators/docker.py
@@ -152,7 +152,7 @@ class DockerOperator(BaseOperator):
     :type retrieve_output_path: Optional[str]
     """
 
-    template_fields = ('image', 'command', 'environment', 'container_name')
+    template_fields: Iterable[str] = ('image', 'command', 'environment', 'container_name')
     template_ext = (
         '.sh',
         '.bash',
@@ -281,6 +281,8 @@ def _run_image_with_mounts(self, target_mounts, add_tmp_variable: bool) -> Optio
             self.environment['AIRFLOW_TMP_DIR'] = self.tmp_dir
         else:
             self.environment.pop('AIRFLOW_TMP_DIR', None)
+        if not self.cli:
+            raise Exception("The 'cli' should be initialized before!")
         self.container = self.cli.create_container(
             command=self.format_command(self.command),
             name=self.container_name,