Use is_matryoshka to denote whether a model is compatible with Matryoshka Representation Learning (MRL).

config.json

@@ -31,5 +31,6 @@
   "type_vocab_size": 1,
   "unpad_inputs": "true",
   "use_memory_efficient_attention": "true",
+  "is_matryoshka": true,
   "vocab_size": 250048
 }