diff --git a/api/server/__init__.py b/api/server/__init__.py
index e69de29..ff892ce 100644
--- a/api/server/__init__.py
+++ b/api/server/__init__.py
@@ -0,0 +1 @@
+from .server import app
diff --git a/api/server/routes/aas_registry_server.py b/api/server/routes/aas_registry_server.py
index 647aef4..81d5db3 100644
--- a/api/server/routes/aas_registry_server.py
+++ b/api/server/routes/aas_registry_server.py
@@ -4,7 +4,7 @@
 from fastapi import APIRouter, Request, HTTPException
 
 from basyx import ObjectStore
-from services.aas_registry_server_service import AasRegistryServerService
+from ..services.aas_registry_server_service import AasRegistryServerService
 
 
 class AasRegistryRouter:
diff --git a/api/server/routes/aasx_file_server.py b/api/server/routes/aasx_file_server.py
index 69e4c39..f0d8df1 100644
--- a/api/server/routes/aasx_file_server.py
+++ b/api/server/routes/aasx_file_server.py
@@ -4,7 +4,7 @@
 from fastapi import APIRouter, Request, HTTPException
 
 from basyx import ObjectStore
-from services.aasx_flie_server_service import AasxFileServerService
+from ..services.aasx_flie_server_service import AasxFileServerService
 
 
 class AasxFileServerRouter:
diff --git a/api/server/routes/submodel.py b/api/server/routes/submodel.py
index 3365508..c59f977 100644
--- a/api/server/routes/submodel.py
+++ b/api/server/routes/submodel.py
@@ -4,7 +4,7 @@
 from fastapi import APIRouter, Request, HTTPException
 
 from basyx import ObjectStore
-from services.submodel_service import SubmodelService
+from ..services.submodel_service import SubmodelService
 
 
 class SubmodelRouter:
diff --git a/api/server/routes/submodel_registry_server.py b/api/server/routes/submodel_registry_server.py
index c9b39b6..dd2640d 100644
--- a/api/server/routes/submodel_registry_server.py
+++ b/api/server/routes/submodel_registry_server.py
@@ -4,7 +4,7 @@
 from fastapi import APIRouter, Request, HTTPException
 
 from basyx import ObjectStore
-from services.submodel_registry_server_service import SubmodelRegistryServerService
+from ..services.submodel_registry_server_service import SubmodelRegistryServerService
 
 
 class SubmodelRegistryRouter:
diff --git a/api/server/server.py b/api/server/server.py
index 0e15fb6..af33fcb 100644
--- a/api/server/server.py
+++ b/api/server/server.py
@@ -2,7 +2,7 @@
 import uvicorn
 
 # Import routers
-from routes import submodel, aasx_file_server, aas_registry_server, submodel_registry_server
+from .routes import submodel, aasx_file_server, aas_registry_server, submodel_registry_server
 
 from basyx import object_store
 
diff --git a/api/test/test_server.py b/api/test/test_server.py
new file mode 100644
index 0000000..bbac675
--- /dev/null
+++ b/api/test/test_server.py
@@ -0,0 +1,17 @@
+import unittest
+from fastapi.testclient import TestClient
+from server import app  # Import your FastAPI app
+
+# Create a TestClient instance for your app
+client = TestClient(app)
+
+class TestFastAPIEndpoints(unittest.TestCase):
+    def test_registry_submodel_descriptors(self):
+        # Test the GET /items/{item_id} endpoint
+        response = client.get("/api/v3.0/submodels/")
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.json(), [])
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/sdk/basyx/object_store.py b/sdk/basyx/object_store.py
index 090b486..851e5ec 100644
--- a/sdk/basyx/object_store.py
+++ b/sdk/basyx/object_store.py
@@ -190,16 +190,16 @@ def get_parent_referable(self, id_short: str) -> Referable:
                         return element
         raise KeyError("there is no parent Identifiable for id_short {}".format(id_short))
 
-    def filter_identifiables_by_instance(self, instance: Type) -> list[Type]:
+    def get_identifiables_by_type(self, t: Type) -> list[Type]:
         """
         Get all identifiables of the specified type.
 
-        :param instance: The Type to filter by. For example, we can filter by "aas_core3.types.ConceptDescription"
+        :param t: The Type to filter by. For example, we can filter by "aas_core3.types.ConceptDescription"
         :return: The list of the filtered identifiables
         """
         filtered_identifiables = []
         for identifiable in self._backend.values():
-            if isinstance(identifiable, instance):
+            if isinstance(identifiable, t):
                 filtered_identifiables.append(identifiable)
         return filtered_identifiables