Fix all outstanding flake8 issues (#4535)

torchvision/datasets/cifar.py

@@ -4,7 +4,6 @@ import pickle
 from typing import Any, Callable, Optional, Tuple
 
 import numpy as np
-import torch
 from PIL import Image
 
 from .utils import check_integrity, download_and_extract_archive

torchvision/datasets/widerface.py

@@ -6,7 +6,6 @@ import torch
 from PIL import Image
 
 from .utils import (
-    check_integrity,
     download_file_from_google_drive,
     download_and_extract_archive,
     extract_archive,

torchvision/io/_video_opt.py

 import math
-import os
 import warnings
 from fractions import Fraction
 from typing import List, Tuple

torchvision/models/densenet.py

@@ -65,11 +65,11 @@ class _DenseLayer(nn.Module):
         return cp.checkpoint(closure, *input)
 
     @torch.jit._overload_method  # noqa: F811
-    def forward(self, input: List[Tensor]) -> Tensor:
+    def forward(self, input: List[Tensor]) -> Tensor:  # noqa: F811
         pass
 
     @torch.jit._overload_method  # noqa: F811
-    def forward(self, input: Tensor) -> Tensor:
+    def forward(self, input: Tensor) -> Tensor:  # noqa: F811
         pass
 
     # torchscript does not yet support *args, so we overload method

torchvision/models/detection/rpn.py

@@ -9,7 +9,7 @@ from torchvision.ops import boxes as box_ops
 from . import _utils as det_utils
 
 # Import AnchorGenerator to keep compatibility.
-from .anchor_utils import AnchorGenerator
+from .anchor_utils import AnchorGenerator  # noqa: 401
 from .image_list import ImageList
 
 

torchvision/models/detection/ssdlite.py

 import warnings
 from collections import OrderedDict
 from functools import partial
-from typing import Any, Callable, Dict, List, Optional, Tuple
+from typing import Any, Callable, Dict, List, Optional
 
 import torch
 from torch import nn, Tensor

torchvision/models/mobilenetv2.py

 import warnings
-from functools import partial
 from typing import Callable, Any, Optional, List
 
 import torch

torchvision/ops/_register_onnx_ops.py

@@ -7,12 +7,7 @@ _onnx_opset_version = 11
 
 
 def _register_custom_op():
-    from torch.onnx.symbolic_helper import (
-        parse_args,
-        scalar_type_to_onnx,
-        scalar_type_to_pytorch_type,
-        cast_pytorch_to_onnx,
-    )
+    from torch.onnx.symbolic_helper import parse_args
     from torch.onnx.symbolic_opset11 import select, squeeze, unsqueeze
     from torch.onnx.symbolic_opset9 import _cast_Long