Allow passing a list to Bundle constructor

Fix #26

stix2/bundle.py

@@ -17,6 +17,9 @@ class Bundle(_STIXBase):
     def __init__(self, *args, **kwargs):
         # Add any positional arguments to the 'objects' kwarg.
         if args:
-            kwargs['objects'] = kwargs.get('objects', []) + list(args)
+            if isinstance(args[0], list):
+                kwargs['objects'] = args[0] + list(args[1:]) + kwargs.get('objects', [])
+            else:
+                kwargs['objects'] = list(args) + kwargs.get('objects', [])
 
         super(Bundle, self).__init__(**kwargs)

stix2/test/test_bundle.py

@@ -92,3 +92,27 @@ def test_create_bundle_with_positional_args(indicator, malware, relationship):
     bundle = stix2.Bundle(indicator, malware, relationship)
 
     assert str(bundle) == EXPECTED_BUNDLE
+
+
+def test_create_bundle_with_positional_listarg(indicator, malware, relationship):
+    bundle = stix2.Bundle([indicator, malware, relationship])
+
+    assert str(bundle) == EXPECTED_BUNDLE
+
+
+def test_create_bundle_with_listarg_and_positional_arg(indicator, malware, relationship):
+    bundle = stix2.Bundle([indicator, malware], relationship)
+
+    assert str(bundle) == EXPECTED_BUNDLE
+
+
+def test_create_bundle_with_listarg_and_kwarg(indicator, malware, relationship):
+    bundle = stix2.Bundle([indicator, malware], objects=[relationship])
+
+    assert str(bundle) == EXPECTED_BUNDLE
+
+
+def test_create_bundle_with_arg_listarg_and_kwarg(indicator, malware, relationship):
+    bundle = stix2.Bundle([indicator], malware, objects=[relationship])
+
+    assert str(bundle) == EXPECTED_BUNDLE