Update tf-metadata.json

source/tf-metadata.json

@@ -2208,7 +2208,7 @@
     "schema": {
       "attributes": [
         {
-          "description": "Must be one of the following: `int8`, `int16`, `int32`, `int64`, `complex64`, `complex128`, `float32`, `float64`, `bool`.",
+          "description": "Must be one of the following: `int8`, `int16`, `int32`, `int64`, `complex64`, `complex128`, `float32`, `float64`, `bool`, `variant`.",
           "name": "T",
           "type": "type"
         },