diff --git a/src/adam/model/model.py b/src/adam/model/model.py
index 4c1f9299..5d34a62f 100644
--- a/src/adam/model/model.py
+++ b/src/adam/model/model.py
@@ -124,24 +124,24 @@ def get_joints_chain(self, root: str, target: str) -> List[Joint]:
             List[Joint]: the list of the joints
         """
 
-        if target not in list(self.links) and target not in list(self.frames):
+        if target not in list(self.links) and target not in list(self.tree.graph):
             raise ValueError(f"{target} is not not in the robot model.")
 
         if target == root:
             return []
         chain = []
-        current_node = [
+        current_joint = [
             joint for joint in self.joints.values() if joint.child == target
         ][0]
 
-        chain.insert(0, current_node)
-        while current_node.parent != root:
-            current_node = [
+        chain.insert(0, current_joint)
+        while current_joint.parent != root:
+            current_joint = [
                 joint
                 for joint in self.joints.values()
-                if joint.child == current_node.parent
+                if joint.child == current_joint.parent
             ][0]
-            chain.insert(0, current_node)
+            chain.insert(0, current_joint)
         return chain
 
     def get_total_mass(self) -> float:
diff --git a/src/adam/model/std_factories/std_model.py b/src/adam/model/std_factories/std_model.py
index ffeff713..bf3c3e75 100644
--- a/src/adam/model/std_factories/std_model.py
+++ b/src/adam/model/std_factories/std_model.py
@@ -17,10 +17,7 @@ def urdf_remove_sensors_tags(xml_string):
     for sensors_tag in root.findall("sensor"):
         root.remove(sensors_tag)
 
-    # Convert the modified XML back to a string
-    modified_xml_string = ET.tostring(root)
-
-    return modified_xml_string
+    return ET.tostring(root)
 
 
 class URDFModelFactory(ModelFactory):
@@ -44,9 +41,8 @@ def __init__(self, path: str, math: SpatialMath):
         # to have a useless and noisy warning, let's remove before hands all the sensor elements,
         # that anyhow are not parser by urdf_parser_py or adam
         # See https://github.com/ami-iit/ADAM/issues/59
-        xml_file = open(path, "r")
-        xml_string = xml_file.read()
-        xml_file.close()
+        with open(path, "r") as xml_file:
+            xml_string = xml_file.read()
         xml_string_without_sensors_tags = urdf_remove_sensors_tags(xml_string)
         self.urdf_desc = urdf_parser_py.urdf.URDF.from_xml_string(
             xml_string_without_sensors_tags