Remove numpy dependency from onnx (pytorch#159177)

One should not expect numpy to be there during onnx import
Forward fix for : pytorch#157734
Added regression test to `test_without_numpy` function

Test plan: Run `python -c "import sys;sys.path.insert(0, 'fake_numpy');import torch; import torch.onnx"` with/without this fix
Pull Request resolved: pytorch#159177
Approved by: https://github.com/atalman, https://github.com/justinchuby, https://github.com/titaiwangms, https://github.com/cyyever, https://github.com/Skylion007, https://github.com/andrewboldi

Author: malfet

.ci/pytorch/test.sh

@@ -974,6 +974,8 @@ test_without_numpy() {
   if [[ "${TEST_CONFIG}" == *dynamo_wrapped* ]]; then
     python -c "import sys;sys.path.insert(0, 'fake_numpy');import torch;torch.compile(lambda x:print(x))('Hello World')"
   fi
+  # Regression test for https://github.com/pytorch/pytorch/pull/157734 (torch.onnx should be importable without numpy)
+  python -c "import sys;sys.path.insert(0, 'fake_numpy');import torch; import torch.onnx"
   popd
 }
 

torch/onnx/_internal/exporter/_onnx_program.py

@@ -15,8 +15,6 @@
 import warnings
 from typing import Any, Callable, TYPE_CHECKING
 
-import numpy as np
-
 import torch
 from torch.onnx._internal._lazy_import import onnx, onnxscript_apis, onnxscript_ir as ir
 from torch.onnx._internal.exporter import _dynamic_shapes, _ir_passes
@@ -121,6 +119,7 @@ def _create_value_mapping(graph: ir.Graph) -> dict[str, ir.Value]:
 
 def _to_ort_value(input: torch.Tensor | int | float | str | bool) -> ort.OrtValue:
     """Convert a PyTorch tensor to an ONNX Runtime OrtValue."""
+    import numpy as np
     import onnxruntime as ort
 
     from torch.onnx._internal.exporter import _core