style: PR feedback

Author: yt-ms

src/structurizr/model/deployment_node.py

@@ -15,7 +15,7 @@
 
 """Provide a deployment node model."""
 
-from typing import TYPE_CHECKING, Iterable, List, Union
+from typing import TYPE_CHECKING, Iterable, List, Optional, Union
 
 from pydantic import Field
 
@@ -94,7 +94,7 @@ class DeploymentNode(DeploymentElement):
     def __init__(
         self,
         *,
-        parent: "DeploymentNode" = None,
+        parent: Optional["DeploymentNode"] = None,
         technology: str = "",
         instances: int = 1,
         children: Iterable["DeploymentNode"] = (),

src/structurizr/model/model.py

@@ -120,20 +120,26 @@ def __contains__(self, element: Element):
     @property
     def software_systems(self) -> Set[SoftwareSystem]:
         """Return the software systems in the model."""
-        return {e for e in self.get_elements() if isinstance(e, SoftwareSystem)}
+        return {
+            element
+            for element in self.get_elements()
+            if isinstance(element, SoftwareSystem)
+        }
 
     @property
     def people(self) -> Set[Person]:
         """Return the people in the model."""
-        return {e for e in self.get_elements() if isinstance(e, Person)}
+        return {
+            element for element in self.get_elements() if isinstance(element, Person)
+        }
 
     @property
     def deployment_nodes(self) -> Set[DeploymentNode]:
         """Return the *top level* deployment nodes in the model."""
         return {
-            e
-            for e in self.get_elements()
-            if isinstance(e, DeploymentNode) and e.parent is None
+            element
+            for element in self.get_elements()
+            if isinstance(element, DeploymentNode) and element.parent is None
         }
 
     @classmethod