Add preliminary implementation to load DeviceMetadata from data.

code/iottb/models/device_metadata_model.py

@@ -7,6 +7,7 @@ from typing import Optional, List, Any
 # iottb modules
 from iottb.definitions import ReturnCodes, DEVICE_METADATA_FILE
 from iottb.logger import logger
+
 # 3rd party libs
 
 IMMUTABLE_FIELDS = {"device_name", "device_short_name", "device_id", "date_created"}
@@ -62,10 +63,10 @@ class DeviceMetadata:
             json.dump(metadata, file)
             return ReturnCodes.SUCCESS
 
-
     @classmethod
     def from_json(cls, metadata_json):
-        pass
+        if isinstance(metadata_json, dict):
+            return DeviceMetadata(**metadata_json)
 
     def to_json(self, indent=2):
         # TODO: atm almost exact copy as in CaptureMetadata