[NFC] polish colossalai/testing/comparison.py code style. (#1558)

colossalai/testing/comparison.py

@@ -7,15 +7,19 @@ from torch.distributed import ProcessGroup
 def assert_equal(a: Tensor, b: Tensor):
     assert torch.all(a == b), f'expected a and b to be equal but they are not, {a} vs {b}'
 
+
 def assert_not_equal(a: Tensor, b: Tensor):
     assert not torch.all(a == b), f'expected a and b to be not equal but they are, {a} vs {b}'
 
+
 def assert_close(a: Tensor, b: Tensor, rtol: float = 1e-5, atol: float = 1e-8):
     assert torch.allclose(a, b, rtol=rtol, atol=atol), f'expected a and b to be close but they are not, {a} vs {b}'
 
+
 def assert_close_loose(a: Tensor, b: Tensor, rtol: float = 1e-3, atol: float = 1e-3):
     assert_close(a, b, rtol, atol)
 
+
 def assert_equal_in_group(tensor: Tensor, process_group: ProcessGroup = None):
     # all gather tensors from different ranks
     world_size = dist.get_world_size(process_group)
@@ -25,5 +29,5 @@ def assert_equal_in_group(tensor: Tensor, process_group: ProcessGroup = None):
     # check if they are equal one by one
     for i in range(world_size - 1):
         a = tensor_list[i]
-        b = tensor_list[i+1]
+        b = tensor_list[i + 1]
         assert torch.all(a == b), f'expected tensors on rank {i} and {i+1} to be equal but they are not, {a} vs {b}'