Fix two typos

ignite/metrics/metric_group.py

@@ -1,4 +1,6 @@
-from typing import Any, Callable, Dict
+from typing import Any, Callable, Dict, Sequence
+
+import torch
 
 from ignite.metrics import Metric
 
@@ -18,7 +20,7 @@ class MetricGroup(Metric):
         We construct a group of metrics, attach them to the engine at once and retrieve their result.
 
         .. code-block:: python
-            metric_group = {'acc': Accuracy(), 'precision': Precision(), 'loss': Loss(nn.NLLLoss())}
+            metric_group = MetricGroup({'acc': Accuracy(), 'precision': Precision(), 'loss': Loss(nn.NLLLoss())})
             metric_group.attach(default_evaluator, "eval_metrics")
             y_true = torch.tensor([1, 0, 1, 1, 0, 1])
             y_pred = torch.tensor([1, 0, 1, 0, 1, 1])
@@ -41,7 +43,7 @@ def reset(self):
         for m in self.metrics.values():
             m.reset()
 
-    def update(self, output):
+    def update(self, output: Sequence[torch.Tensor]):
         for m in self.metrics.values():
             m.update(m._output_transform(output))