Unflatten for by benbowen

unflatten does not support lists, the github user benbowen created an
issue: ianlini#8 and described a
solution that worked for him.

src/flatten_dict/flatten_dict.py

@@ -101,11 +101,25 @@ def nested_set_dict(d, keys, value):
     assert keys
     key = keys[0]
     if len(keys) == 1:
-        if key in d:
-            raise ValueError("duplicated key '{}'".format(key))
-        d[key] = value
+        if type(d) == list:
+            d.append(value)
+        else:
+            d[key] = value
         return
-    d = d.setdefault(key, {})
+
+    # the type is a string so make a dict if none exists
+    if type(keys[1]) == int:
+        if key in d:
+            pass
+        else:
+            d[key] = []
+        d = d[key]
+    elif type(key)==int:
+        if (key+1) > len(d):
+            d.append({})
+        d = d[key]
+    else:
+        d = d.setdefault(key, {})
     nested_set_dict(d, keys[1:], value)