chg: Allow to pass an AbstractMISP to add_reference

Fix #379

pymisp/mispevent.py

@@ -1076,6 +1076,9 @@ class MISPObject(AbstractMISP):
 
     def add_reference(self, referenced_uuid, relationship_type, comment=None, **kwargs):
         """Add a link (uuid) to an other object"""
+        if isinstance(referenced_uuid, AbstractMISP):
+            # Allow to pass an object or an attribute instead of its UUID
+            referenced_uuid = referenced_uuid.uuid
         if kwargs.get('object_uuid'):
             # Load existing object
             object_uuid = kwargs.pop('object_uuid')

tests/test_mispevent.py

@@ -82,7 +82,7 @@ class TestMISPEvent(unittest.TestCase):
         del a.uuid
         self.mispevent.objects[0].uuid = 'a'
         self.mispevent.objects[1].uuid = 'b'
-        self.mispevent.objects[0].add_reference('b', 'baz', comment='foo')
+        self.mispevent.objects[0].add_reference(self.mispevent.objects[1], 'baz', comment='foo')
         self.assertEqual(self.mispevent.objects[0].references[0].relationship_type, 'baz')
         with open('tests/mispevent_testfiles/event_obj_attr_tag.json', 'r') as f:
             ref_json = json.load(f)