diff --git a/abcd/__init__.py b/abcd/__init__.py
index 994afcd8..081e868c 100644
--- a/abcd/__init__.py
+++ b/abcd/__init__.py
@@ -40,7 +40,8 @@ def from_url(cls, url, **kwargs):
 
             return MongoDatabase(db_name=db, **conn_settings, **kwargs)
 
-        if r.scheme == "opensearch":
+        r.scheme = ConnectionType[r.scheme]
+        if r.scheme is ConnectionType.opensearch:
             conn_settings = {
                 "host": r.hostname,
                 "port": r.port,
diff --git a/abcd/backends/atoms_opensearch.py b/abcd/backends/atoms_opensearch.py
index bb1eb1af..78af1b08 100644
--- a/abcd/backends/atoms_opensearch.py
+++ b/abcd/backends/atoms_opensearch.py
@@ -196,7 +196,7 @@ def save(self):
             if not self._id:
                 self._client.index(index=self._index_name, body=body)
             else:
-                body.pop("_id", None)
+                del body["_id"]
                 body = {"doc": body}
                 self._client.update(index=self._index_name, id=self._id, body=body)
 
@@ -281,11 +281,11 @@ def __init__(
             info = self.client.info()
             logger.info("DB info: %s", info)
 
-        except AuthenticationException:
-            raise abcd.errors.AuthenticationError()
+        except AuthenticationException as err:
+            raise abcd.errors.AuthenticationError() from err
 
-        except ConnectionTimeout:
-            raise abcd.errors.TimeoutError()
+        except ConnectionTimeout as err:
+            raise abcd.errors.TimeoutError() from err
 
         self.db = db_name
         self.index_name = index_name
@@ -677,9 +677,9 @@ def count_property(self, name, query: Union[dict, str, None] = None) -> dict:
 
         prop = {}
 
-        for val in self.client.search(index=self.index_name, body=body,)[
-            "aggregations"
-        ][format(name)]["buckets"]:
+        for val in self.client.search(
+                index=self.index_name, body=body
+        )["aggregations"][format(name)]["buckets"]:
             prop[val["key"]] = val["doc_count"]
 
         return prop
@@ -728,8 +728,7 @@ def properties(self, query: Union[dict, str, None] = None) -> dict:
                 body=body,
             )
 
-            derived = ["info_keys", "derived_keys", "arrays_keys"]
-            for label in derived:
+            for label in ("info_keys", "derived_keys", "arrays_keys"):
                 count = res["aggregations"][label]["doc_count"]
                 if count > 0:
                     key = label.split("_", maxsplit=1)[0]
@@ -824,8 +823,7 @@ def count_properties(self, query: Union[dict, str, None] = None) -> dict:
                 body=body,
             )
 
-            derived = ["info_keys", "derived_keys", "arrays_keys"]
-            for label in derived:
+            for label in ("info_keys", "derived_keys", "arrays_keys"):
                 count = res["aggregations"][label]["doc_count"]
                 if count > 0:
                     properties[key] = {
@@ -980,9 +978,9 @@ def __repr__(self):
             host, port = None, None
 
         return (
-            "{}(".format(self.__class__.__name__)
-            + "url={}:{}, ".format(host, port)
-            + "index={}) ".format(self.index_name)
+            f"{self.__class__.__name__}("
+            f"url={host}:{port}, "
+            f"index={self.index_name}) "
         )
 
     def _repr_html_(self):
diff --git a/abcd/backends/atoms_properties.py b/abcd/backends/atoms_properties.py
index 5503c398..5ce1ccb2 100644
--- a/abcd/backends/atoms_properties.py
+++ b/abcd/backends/atoms_properties.py
@@ -95,7 +95,7 @@ def __init__(
         self.df.replace({np.nan: None}, inplace=True)
 
         if units is not None:
-            for key in units.keys():
+            for key in units:
                 if key not in self.df.columns.values:
                     raise ValueError(
                         f"Invalid field name: {key}. Keys in `units` must "
@@ -109,20 +109,19 @@ def __init__(
 
         self.store_struct_file = store_struct_file
         if self.store_struct_file:
-            if struct_file_template is not None:
-                self.struct_file_template = struct_file_template
-            else:
+            if struct_file_template is None:
                 raise ValueError(
                     "`struct_file_template` must be specified if "
                     "store_struct_file is True."
                 )
-            if struct_name_label is not None:
-                self.struct_name_label = struct_name_label
-            else:
+            self.struct_file_template = struct_file_template
+
+            if struct_name_label is None:
                 raise ValueError(
                     "`struct_name_label` must be specified if store_struct_file is"
                     " True."
                 )
+            self.struct_name_label = struct_name_label            
             self.set_struct_files()
 
     def _separate_units(self):