Update GenMix50k.py

GenMix50k.py

@@ -83,6 +83,6 @@ class GenMix50k(ds.GeneratorBasedBuilder):
 
     def _generate_examples(self, filepath):
         with open(filepath, encoding="utf-8") as f:
-            for idx, line in enumerate(f):
-                example = json.loads(line)
+            data = json.load(f)
+            for idx, example in enumerate(data):
                 yield idx, example