#31 API Improvement

* adds support for returning all shared data
* adds documentation

api/utils/serializer/v1/serializer.py

@@ -50,6 +50,8 @@ class AbstractModelAPISerializerV1(AbstractModelAPISerializer):
         Returns:
             serialized_json (dict)
         """
+        if konova_code is None:
+            return None
         return {
             "atom_id": konova_code.atom_id,
             "long_name": konova_code.long_name,
@@ -83,7 +85,7 @@ class AbstractModelAPISerializerV1(AbstractModelAPISerializer):
         Returns:
             created_on (timestamp)
         """
-        return entry.created.timestamp
+        return entry.created.timestamp if entry.created is not None else None
 
     def modified_on_to_json(self, entry):
         """ Serializes the modified_on into json
@@ -95,7 +97,7 @@ class AbstractModelAPISerializerV1(AbstractModelAPISerializer):
             modified_on (timestamp)
         """
         modified_on = entry.modified or entry.created
-        modified_on = modified_on.timestamp
+        modified_on = modified_on.timestamp if modified_on is not None else None
         return modified_on