Empty list is a useless function (#475)

* Empty list is a useless function

* trigger tests to make sure test_data works

* change call to 'list' because of tests taking suspiciously long
Co-authored-by: Farhad Ramezanghorbani <farhadrgh@users.noreply.github.com>

torchani/utils.py

@@ -8,12 +8,8 @@ from torchani.units import sqrt_mhessian2invcm, sqrt_mhessian2milliev, mhessian2
 from .nn import SpeciesEnergies
 
 
-def empty_list():
-    return []
-
-
 def stack_with_padding(properties, padding):
-    output = defaultdict(empty_list)
+    output = defaultdict(list)
     for p in properties:
         for k, v in p.items():
             output[k].append(torch.as_tensor(v))