Added pickle support for Resource classes, albeit a bit hacky.

Unpickling requires the class to be known, so we can't simply use to_dict()
to pickle and pass the dict to __init__() to unpickle. This works for the
pickled object itself (as pickle restores its type), but fails to restore
the class of subobjects, such as some_node.picture. This is why the code
now pickles each subobject too.

pillarsdk/resource.py

@@ -140,6 +140,53 @@ class Resource(object):
 
         return cls(dict_or_resource)
 
+    def __getstate__(self):
+        """Returns a state suitable for pickling.
+
+        This is basically a copy of to_dict(), except that subobjects
+        are pickled instead of stored as sub-dict.
+        """
+        import pickle
+
+        def parse_object(value):
+            if isinstance(value, Resource):
+                return '__pickled__', pickle.dumps(value)
+            elif isinstance(value, list):
+                new_list = []
+                for obj in value:
+                    new_list.append(parse_object(obj))
+                return new_list
+            else:
+                return value
+
+        data = {}
+        for key in self.__data__:
+            data[key] = parse_object(self.__data__[key])
+        return data
+
+    def __setstate__(self, state):
+        import pickle
+
+        def is_pickled(subval):
+            return (isinstance(subval, tuple)
+                    and len(subval) == 2
+                    and subval[0] == '__pickled__'
+                    and isinstance(subval[1], bytes))
+
+        for key, val in state.items():
+            if is_pickled(val):
+                state[key] = pickle.loads(val[1])
+            elif isinstance(val, list):
+                for idx, subval in enumerate(val):
+                    if is_pickled(subval):
+                        val[idx] = pickle.loads(subval[1])
+            elif isinstance(val, dict):
+                for subkey, subval in val.items():
+                    if is_pickled(subval):
+                        val[subkey] = pickle.loads(subval[1])
+
+        self.__init__(state)
+
 
 class Find(Resource):
     @classmethod