🐛 [Bug] AttributeError: '_OpNamespace' 'tensorrt' object has no attribute 'quantize_op'

[HolyWu]

Bug Description

An error was thrown when nvidia-modelopt was not installed, albeit it was not used at all.

Traceback (most recent call last):
  File "/home/holywu/test.py", line 11, in <module>
    trt_model = torch_tensorrt.dynamo.compile(
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch_tensorrt/dynamo/_compiler.py", line 697, in compile
    gm = post_lowering(gm, settings)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch_tensorrt/dynamo/lowering/passes/_aten_lowering_pass.py", line 102, in post_lowering
    gm = ATEN_POST_LOWERING_PASSES(gm, settings)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch_tensorrt/dynamo/lowering/passes/pass_manager.py", line 56, in __call__
    out = _pass(out, settings)
          ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/contextlib.py", line 81, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch_tensorrt/dynamo/lowering/passes/constant_folding.py", line 34, in constant_fold
    cf.run()
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch/_inductor/constant_folding.py", line 280, in run
    return super().run(initial_env=env)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch/fx/interpreter.py", line 171, in run
    self.env[node] = self.run_node(node)
                     ^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch/_inductor/constant_folding.py", line 252, in run_node
    if self.is_impure(node):
       ^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch_tensorrt/dynamo/lowering/passes/constant_folding.py", line 104, in is_impure
    if node.target in (torch.ops.tensorrt.quantize_op.default,):
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/holywu/torch_2.8.dev/lib/python3.12/site-packages/torch/_ops.py", line 1317, in __getattr__
    raise AttributeError(
AttributeError: '_OpNamespace' 'tensorrt' object has no attribute 'quantize_op'

To Reproduce

import torch
import torch_tensorrt
import torchvision.models as models


with torch.inference_mode():
    model = models.resnet18(weights=models.ResNet18_Weights.IMAGENET1K_V1).eval().cuda()
    inputs = (torch.randn(1, 3, 224, 224, device="cuda"),)
    exported_program = torch.export.export(model, inputs)

    trt_model = torch_tensorrt.dynamo.compile(
        exported_program,
        inputs,
        min_block_size=1,
    )

Environment

• Torch-TensorRT Version (e.g. 1.0.0): 2.8.0.dev20250607+cu128
• PyTorch Version (e.g. 1.0): 2.8.0.dev20250607+cu128
• CPU Architecture: x64
• OS (e.g., Linux): Ubuntu 24.04 LTS
• How you installed PyTorch (conda, pip, libtorch, source): pip
• Build command you used (if compiling from source):
• Are you using local sources or building from archives:
• Python version: 3.12.3
• CUDA version: 12.8
• GPU models and configuration: RTX 4060 Ti
• Any other relevant information:

Additional context

Probably introduced by #3543

[lanluo-nvidia]

@HolyWu Thanks for reporting the bug,
please review #3562