`nn.graph` doesn't have helpful error message for incorrect arguments

[jackalcooper]

Summary

• It raises:

NotImplementedError: nn.Graph.build()'s input/output item only support types: Tensor/None.

• Not helpful. It would be much useful if the type not supported or index of argument is reported.

Code to reproduce bug

When type of argument is not supported by nn.graph

System Information

• What is your OneFlow installation (pip, source, dockerhub):
• OS:
• OneFlow version (run python3 -m oneflow --doctor):
• Python version:
• CUDA driver version:
• GPU models:
• Other info: