Set error feature as sequence of sequences

icelandic-error-corpus-IceEC.py

@@ -818,7 +818,7 @@ class IceEC(datasets.GeneratorBasedBuilder):
                 {
                     "idx": datasets.Value("string"),
                     "sentence": datasets.Sequence(datasets.Value("string")),
-                    "errors": datasets.Sequence(datasets.Value("string"))
+                    "errors": datasets.Sequence(datasets.Sequence(datasets.Value("string")))
                 }
             ),
             # No default supervised_keys (as we have to pass both question