Default argument not captured in FX graph

When I torch.export the sample module in the official tutorial:

import torch
from torch.export import export

class MyModule(torch.nn.Module):
    def __init__(self):
        self.lin = torch.nn.Linear(100, 10)

    def forward(self, x, y):
        return torch.nn.functional.relu(self.lin(x + y), inplace=True)

mod = MyModule()
exported_mod = export(mod, (torch.randn(8, 100), torch.randn(8, 100)))
print(exported_mod(torch.randn(8, 100), torch.randn(8, 100)))

The resulting graph doesn’t capture the default value of the alpha parameter for the sum x + y:

    %add : [num_users=1] = call_function[target=torch.ops.aten.add.Tensor](args = (%arg2_1, %arg3_1), kwargs = {})

By contrast if I explicitly pass in alpha

        return torch.nn.functional.relu(self.lin(torch.add(x, y, alpha = 0.5)), inplace=True)

Then the graph correctly contains the third argument

    %add : [num_users=1] = call_function[target=torch.ops.aten.add.Tensor](args = (%arg2_1, %arg3_1), kwargs = {alpha: 0.5})

Not including the default value of the argument (when the argument is left unspecified by the caller) is a problem for backends that want to work with the FX graph, because it means that the backend has to reach out of the FX graph to find out the default value.

This is what e.g. the shark-turbine importer does in

Instead of iterating over e.g. the arguments of a call_function node, they get a FunctionSchema from the node (a protected field) and iterate over that.

This seems like a bug in torch.export since it breaks encapsulation. Thoughts?