[core] Change the token parsing part in prevision of different flags.

tests/features/test_not_modified.py

@@ -0,0 +1,24 @@
+from bonobo.constants import NOT_MODIFIED
+from bonobo.util.testing import BufferingNodeExecutionContext
+
+
+def useless(*args, **kwargs):
+    return NOT_MODIFIED
+
+
+def test_not_modified():
+    input_messages = [
+        ('foo', 'bar'),
+        {'foo': 'bar'},
+        ('foo', {'bar': 'baz'}),
+        (),
+    ]
+
+    with BufferingNodeExecutionContext(useless) as context:
+        context.write_sync(*input_messages)
+
+    assert context.get_buffer() == input_messages
+
+
+
+