typing inductor and placeholder backends (#160366)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/160366
Approved by: https://github.com/Skylion007
ghstack dependencies: #160362, #160363, #160364, #160365

torch/_dynamo/backends/inductor.py

@@ -1,5 +1,3 @@
-# mypy: ignore-errors
-
 """
 This module provides the TorchInductor backend integration for TorchDynamo.
 
@@ -12,12 +10,14 @@ The inductor backend can be used with torch.compile():
     model = torch.compile(model, backend="inductor")
 """
 
+from typing import Any
+
 from torch._dynamo import register_backend
 from torch._dynamo.utils import dynamo_timed
 
 
 @register_backend
-def inductor(*args, **kwargs):
+def inductor(*args: Any, **kwargs: Any) -> Any:
     with dynamo_timed("inductor_import", log_pt2_compile_event=True):
         # do import here to avoid loading inductor into memory when it is not used
         # The AsyncCompile subproc pool can be slow to start, so warm it up as early

torch/_dynamo/backends/onnxrt.py

@@ -1,5 +1,3 @@
-# mypy: ignore-errors
-
 # This backend is maintained by ONNX team. To direct issues
 # to the right people, please tag related GitHub issues with `module: onnx`.
 #

torch/_dynamo/backends/tensorrt.py

@@ -1,5 +1,3 @@
-# mypy: ignore-errors
-
 # import torch  # type: ignore[import]
 # from .common import device_from_inputs, fake_tensor_unsupported  # type: ignore[import]
 # from .registry import register_backend  # type: ignore[import]