Fix(Test): Regex format

tests/test_simple_api.py

@@ -47,7 +47,7 @@ class TestApi(unittest.TestCase):
 
         # Success
         result = self.api.build_json(data)
-        result = re.sub('[^a-z0-9\{\}\:"]+', "", result, flags=re.IGNORECASE)
+        result = re.sub(r'[^a-z0-9\{\}\:"]+', "", result, flags=re.IGNORECASE)
         self.assertEqual(json_string, result)
 
         # Check for cleaned up key