diff --git a/src/rules_tree.py b/src/rules_tree.py
index 329b5d7..5ff0b56 100644
--- a/src/rules_tree.py
+++ b/src/rules_tree.py
@@ -13,10 +13,11 @@ for i in range(0, len(model.testmodel.get_conditions().get_conditions_array())):
     condition = model.testmodel.get_conditions().get_condition(i)
     conditions_set.add((condition.get_node_self_id(),
                         condition.get_node_parent_id(),
-                        condition.get_coord("x"), # TODO  y,z,...
+                        condition.get_coord("x"),  # TODO  y,z,...
                         condition.get_site(),
                         condition.get_weight()))
 
+
 class CondTreeNode(NodeMixin):
     def __init__(self, id, x, site, weight, parent_node_id):
         super(CondTreeNode, self).__init__()
@@ -31,12 +32,13 @@ class CondTreeNode(NodeMixin):
         self.parent = parent_node
         print('orphan node ', self.id, ' is adopted by node ', parent_node.id)
 
+
 for i in conditions_set:  # sorted(conditions_set, key=i.id):
     condition = CondTreeNode(i[0], i[2], i[3], i[4], i[1])   # TODO y,z,...
     conditions_list.append(condition)
 
 for i in conditions_list:
-    if (i.parent == None):
+    if (i.parent is None):
         for j in conditions_list:
             if (i.parent_node_id == j.id):
                 i.add_parent_node(j)