more styling fixes:

src/lerobot/processor/observation_processor.py

@@ -290,29 +290,25 @@ class LiberoProcessorStep(ObservationProcessorStep):
         """
 
         if not isinstance(quat, torch.Tensor):
-            raise TypeError(
+            raise TypeError(f"_quat2axisangle expected a torch.Tensor, got {type(quat)}")
-                f"_quat2axisangle expected a torch.Tensor, got {type(quat)}"
-            )
 
         if quat.ndim != 2 or quat.shape[1] != 4:
-            raise ValueError(
+            raise ValueError(f"_quat2axisangle expected shape (B, 4), got {tuple(quat.shape)}")
-                f"_quat2axisangle expected shape (B, 4), got {tuple(quat.shape)}"
-            )
 
         quat = quat.to(dtype=torch.float32)
         device = quat.device
-        B = quat.shape[0]
+        batch_size = quat.shape[0]
 
         w = quat[:, 3].clamp(-1.0, 1.0)
 
         den = torch.sqrt(torch.clamp(1.0 - w * w, min=0.0))
 
-        result = torch.zeros((B, 3), device=device)
+        result = torch.zeros((batch_size, 3), device=device)
 
         mask = den > 1e-10
 
         if mask.any():
-            angle = 2.0 * torch.acos(w[mask])            # (M,)
+            angle = 2.0 * torch.acos(w[mask])  # (M,)
             axis = quat[mask, :3] / den[mask].unsqueeze(1)
             result[mask] = axis * angle.unsqueeze(1)