fix: repair broken torch.nn imports in vggt modules

vggt/heads/track_head.py

@@ -4,7 +4,8 @@
 # This source code is licensed under the license found in the
 # LICENSE file in the root directory of this source tree.
 
-import torch  # Attention computation.nn as nn
+import torch
+import torch.nn as nn
 from .dpt_head import DPTHead
 from .track_modules.base_track_predictor import BaseTrackerPredictor
 

vggt/layers/attention.py

@@ -13,7 +13,8 @@ import warnings
 
 from torch import Tensor
 from torch import nn
-import torch  # Self-attention layers.nn.functional as F
+import torch
+import torch.nn.functional as F
 
 XFORMERS_AVAILABLE = False
 

vggt/models/vggt.py

@@ -4,8 +4,8 @@
 # This source code is licensed under the license found in the
 # LICENSE file in the root directory of this source tree.
 
-import torch  # Core tensor operations
-import torch  # Core tensor operations.nn as nn
+import torch
+import torch.nn as nn
 from huggingface_hub import PyTorchModelHubMixin  # used for model hub
 
 from vggt.models.aggregator import Aggregator

vggt/utils/rotation.py

@@ -6,9 +6,9 @@
 
 # Modified from PyTorch3D, https://github.com/facebookresearch/pytorch3d
 
-import torch  # Rotation matrices
+import torch
+import torch.nn.functional as F
 import numpy as np
-import torch  # Rotation matrices.nn.functional as F
 
 
 def quat_to_mat(quaternions: torch.Tensor) -> torch.Tensor: