json_clean: Prevent making a set containing dict keys

This step eats up CPU cycles on each communication between ipykernel and
the front-end.

Author: martinRenou

ipykernel/jsonutil.py

@@ -123,14 +123,6 @@ def json_clean(obj):
         return [json_clean(x) for x in obj]
 
     if isinstance(obj, dict):
-        # First, validate that the dict won't lose data in conversion due to
-        # key collisions after stringification.  This can happen with keys like
-        # True and 'true' or 1 and '1', which collide in JSON.
-        nkeys = len(obj)
-        nkeys_collapsed = len(set(map(str, obj)))
-        if nkeys != nkeys_collapsed:
-            raise ValueError('dict cannot be safely converted to JSON: '
-                             'key collision would lead to dropped values')
         # If all OK, proceed by making the new dict that will be json-safe
         out = {}
         for k, v in obj.items():