Small fixups

stix2/__init__.py

@@ -194,6 +194,7 @@ class Relationship(_STIXBase):
         'target_ref',
     ]
 
+    # Explicitly define the first three kwargs to make readable Relationship declarations.
     def __init__(self, source_ref=None, relationship_type=None, target_ref=None,
                  **kwargs):
         # TODO:

stix2/test/test_stix2.py

@@ -37,7 +37,6 @@ MALWARE_KWARGS = dict(
     name="Cryptolocker",
 )
 
-
 # Minimum required args for a Relationship instance
 RELATIONSHIP_KWARGS = dict(
     relationship_type="indicates",