fix bug concerning input format

horizon-metrics.py

@@ -138,9 +138,13 @@ class HorizonMetrics(evaluate.Metric):
             # This defines the format of each prediction and reference
             features=datasets.Features({
                 'predictions':
-                datasets.Sequence(datasets.Value("float")),
+                datasets.Sequence(
+                    datasets.Sequence(
+                        datasets.Sequence(datasets.Value("float")))),
                 'references':
-                datasets.Sequence(datasets.Value("float")),
+                datasets.Sequence(
+                    datasets.Sequence(
+                        datasets.Sequence(datasets.Value("float")))),
             }),
             codebase_urls=["http://github.com/path/to/codebase/of/new_module"])