Type mismatch for layer.bias

I’m working on a CNN implementation in PyTorch, in this PR. I’m getting mypy error in CI Test.
The mypy check fails saying :

deepchem/models/torch_models/cnn.py:208: error: Argument 1 to "constant_" has incompatible type "Optional[Tensor]"; expected "Tensor"
Found 1 error in 1 file (checked 364 source files)
Error: Process completed with exit code 1.

I believe the cause of error is :
In ConvNd layers definition in PyTorch source code here , bias has type Optional[Tensor] .

nn.init.constant_ , expects torch.Tensor argument

Is there any way to fix this mypy error ?