Added engine file and separated test code

src/engine.py

@@ -0,0 +1,4 @@
+class Engine:
+    """Calculates a sequence."""
+
+    

src/models.py

@@ -153,7 +153,9 @@ class Flickr:
         return Flickr.schema().loads(json)
 
 
-f = Flickr(
+if __name__ == "__main__":
+    # Small test
+    f = Flickr(
         [
             Space(
                 "iosf",
@@ -186,10 +188,9 @@ f = Flickr(
                 ],
             )
         ],
-)
+    )
 
+    f.save("test.json")
+    a = Flickr.load("test.json")
 
-f.save("test.json")
-a = Flickr.load("test.json")
-
-print(f.to_json())
+    print(f.to_json())