diff --git a/city_model_structure/attributes/edge.py b/city_model_structure/attributes/edge.py
index 14c18c16..3274a969 100644
--- a/city_model_structure/attributes/edge.py
+++ b/city_model_structure/attributes/edge.py
@@ -5,8 +5,9 @@ Copyright © 2020 Project Author Guille Gutierrez guillermo.gutierrezmorote@conc
 Contributor Milad milad.aghamohamadnia@concordia.ca
 """
 import uuid
-from typing import List
-from city_model_structure.attributes.node import Node
+from typing import List, TypeVar
+
+UsageZone = TypeVar('Node')
 
 
 class Edge:
diff --git a/city_model_structure/attributes/node.py b/city_model_structure/attributes/node.py
index e6f4a410..7c366bea 100644
--- a/city_model_structure/attributes/node.py
+++ b/city_model_structure/attributes/node.py
@@ -6,9 +6,9 @@ Contributor Milad milad.aghamohamadnia@concordia.ca
 """
 
 import uuid
-from typing import List
-from city_model_structure.attributes.edge import Edge
+from typing import List, TypeVar
 
+UsageZone = TypeVar('Edge')
 
 class Node:
   """
diff --git a/city_model_structure/attributes/polyhedron.py b/city_model_structure/attributes/polyhedron.py
index a1099547..b468e736 100644
--- a/city_model_structure/attributes/polyhedron.py
+++ b/city_model_structure/attributes/polyhedron.py
@@ -217,7 +217,7 @@ class Polyhedron:
     return self._min_x
 
   @property
-  def centroid(self) -> [float]:
+  def centroid(self) -> List[float]:
     """
     Get polyhedron centroid
     :return: [x,y,z]
diff --git a/city_model_structure/building.py b/city_model_structure/building.py
index b985383e..a7123808 100644
--- a/city_model_structure/building.py
+++ b/city_model_structure/building.py
@@ -59,9 +59,10 @@ class Building(CityObject):
         self._internal_walls.append(surface)
 
   @property
-  def grounds(self) -> [Surface]:
+  def grounds(self) -> List[Surface]:
     """
     Get building ground surfaces
+    :return: [Surface]
     """
     return self._grounds
 
@@ -88,7 +89,7 @@ class Building(CityObject):
     return False
 
   @property
-  def roofs(self) -> [Surface]:
+  def roofs(self) -> List[Surface]:
     """
     Get building roof surfaces
     :return: [Surface]
@@ -96,7 +97,7 @@ class Building(CityObject):
     return self._roofs
 
   @property
-  def walls(self) -> [Surface]:
+  def walls(self) -> List[Surface]:
     """
     Get building wall surfaces
     :return: [Surface]
@@ -286,7 +287,7 @@ class Building(CityObject):
     return self._eave_height
 
   @property
-  def storeys(self) -> [Storey]:
+  def storeys(self) -> List[Storey]:
     """
     Get building storeys
     :return: [Storey]
diff --git a/city_model_structure/building_demand/surface.py b/city_model_structure/building_demand/surface.py
index a6dc6a6b..bb5eb37d 100644
--- a/city_model_structure/building_demand/surface.py
+++ b/city_model_structure/building_demand/surface.py
@@ -236,9 +236,9 @@ class Surface:
     """
     Get hole surfaces, a list of hole polygons found in the surface
     :return: None, [] or [Polygon]
-      None -> not known whether holes exist in reality or not due to low level of detail of input data
-      [] -> no holes in the surface
-      [Polygon] -> one or more holes in the surface
+    None -> not known whether holes exist in reality or not due to low level of detail of input data
+    [] -> no holes in the surface
+    [Polygon] -> one or more holes in the surface
     """
     return self._holes_polygons
 
diff --git a/city_model_structure/city_object.py b/city_model_structure/city_object.py
index c99e137e..9b935e60 100644
--- a/city_model_structure/city_object.py
+++ b/city_model_structure/city_object.py
@@ -122,7 +122,7 @@ class CityObject:
     return None
 
   @property
-  def centroid(self):
+  def centroid(self) -> List[float]:
     """
     Get city object centroid
     :return: [x,y,z]
diff --git a/city_model_structure/iot/sensor.py b/city_model_structure/iot/sensor.py
index 6dfad778..25a79f45 100644
--- a/city_model_structure/iot/sensor.py
+++ b/city_model_structure/iot/sensor.py
@@ -68,6 +68,6 @@ class Sensor:
   @property
   def measures(self):
     """
-    Sensor measures
+    Raises not implemented error
     """
     raise NotImplementedError
diff --git a/imports/schedules/doe_idf.py b/imports/schedules/doe_idf.py
index 746ab47d..8c434850 100644
--- a/imports/schedules/doe_idf.py
+++ b/imports/schedules/doe_idf.py
@@ -5,13 +5,14 @@ Copyright © 2020 Project
 """
 import pandas as pd
 import parseidf
+import xmltodict
 
 
 class DoeIdf:
   """
   Idf factory to import schedules into the data model
   """
-  idf_schedule_to_commet_schedule = {'BLDG_LIGHT_SCH': 'Lights',
+  idf_schedule_to_comnet_schedule = {'BLDG_LIGHT_SCH': 'Lights',
                                      'BLDG_OCC_SCH_wo_SB': 'Occupancy',
                                      'BLDG_EQUIP_SCH': 'Equipment',
                                      'ACTIVITY_SCH': 'Activity',
@@ -44,8 +45,8 @@ class DoeIdf:
   def _load_schedule(self, idf, building_usage):
     schedules_day = {}
     for compact_schedule in idf[self._SCHEDULE_COMPACT_TYPE]:
-      if compact_schedule[self._SCHEDULE_TYPE_NAME] in self.idf_schedule_to_commet_schedule:
-        schedule_type = self.idf_schedule_to_commet_schedule[compact_schedule[self._SCHEDULE_TYPE_NAME]]
+      if compact_schedule[self._SCHEDULE_TYPE_NAME] in self.idf_schedule_to_comnet_schedule:
+        schedule_type = self.idf_schedule_to_comnet_schedule[compact_schedule[self._SCHEDULE_TYPE_NAME]]
       else:
         continue
       days_index = []