diff --git a/explaining_framework/metric/sparsity.py b/explaining_framework/metric/sparsity.py
index ea0ee77..b3f7a61 100644
--- a/explaining_framework/metric/sparsity.py
+++ b/explaining_framework/metric/sparsity.py
@@ -1,24 +1,24 @@
 import torch
+
 from explaining_framework.metric.base import Metric
 
 
 class Sparsity(Metric):
     def __init__(self, name):
         super().__init__(name=name)
-        self.authorized_metric = ['l0']
+        self.authorized_metric = ["l0"]
         self.metric = self.load_metric(name)
 
-    def load_metric(self,name):
+    def load_metric(self, name):
         if name in self.authorized_metric:
-            if name == 'l0':
-                metric = lambda x : torch.mean(mask.float()).item()
+            if name == "l0":
+                metric = lambda x: torch.mean(mask.float()).item()
         else:
-            raise ValueError(f'{name} is not supported yet')
+            raise ValueError(f"{name} is not supported yet")
 
-
-    def forward(self, exp:Explanation) -> float:
+    def forward(self, exp: Explanation) -> float:
         out = {}
-        for k,v in exp.to_dict():
-            if 'mask' in 
-
-        return torch.mean(mask.float()).item()
+        for k, v in exp.to_dict():
+            if "mask" in k and v.dtype == torch.bool:
+                out[k] = torch.mean(mask.float()).item()
+        return out