diff --git a/src/sdx_datamodel/models/topology.py b/src/sdx_datamodel/models/topology.py
index f046ee1..7d4f9c7 100644
--- a/src/sdx_datamodel/models/topology.py
+++ b/src/sdx_datamodel/models/topology.py
@@ -59,11 +59,11 @@ def __init__(
     ):
         """Topology - a model defined in Swagger"""
 
-        self._domain_service = None
-        self._private_attributes = None
         self._id = id
         self._name = name
-        if domain_service is not None:
+        if domain_service is None:
+            self._domain_service = None
+        else:
             self._domain_service = self.set_domain_service(domain_service)
         self._version = version
         self._timestamp = timestamp
@@ -71,8 +71,7 @@ def __init__(
         self._links = []
         self._nodes = self.set_nodes(nodes)
         self._links = self.set_links(links)
-        if private_attributes is not None:
-            self._private_attributes = private_attributes
+        self._private_attributes = private_attributes
 
     @property
     def id(self):
@@ -253,7 +252,7 @@ def add_nodes(self, node_objects):
         self._nodes.extend(node_objects)
 
     def get_node_by_port(self, aPort):
-        for node in self.nodes:
+        for node in self._nodes:
             ports = node.ports
             for port in ports:
                 if port.id == aPort:
@@ -262,7 +261,7 @@ def get_node_by_port(self, aPort):
         return None
 
     def get_port_by_link(self, n1_id, n2_id):
-        for x in self.links:
+        for x in self._links:
             # print("--------")
             # print(x.ports[0]['node'])
             # print(x.ports[1]['node'])
@@ -272,7 +271,7 @@ def get_port_by_link(self, n1_id, n2_id):
                 return n1_id, x.ports[1], n2_id, x.ports[0]
 
     def has_node_by_id(self, id):
-        for node in self.nodes:
+        for node in self._nodes:
             if id == node.id:
                 return True
         return False