Machine learning

Current implementation of Go binding can not specify options.

GPUOptions struct is in internal package. And go generate doesn't work for protobuf directory. So we can't specify GPUOptions for NewSession.

🐛 Bug

--- Logging error ---
Traceback (most recent call last):
  File "/scratch/rzou/pt/workspace-env/lib/python3.7/logging/__init__.py", line 1025, in emit
    msg = self.format(record)
  File "/scratch/rzou/pt/workspace-env/lib/python3.7/logging/__init__.py", line 869, in format
    return fmt.format(record)
  File "/scratch/rzou/pt/workspace-env/lib/python3.7/site-packages/_pytes

I just discover that we have a helper function to validate scalar:
https://scikit-learn.org/stable/modules/generated/sklearn.utils.check_scalar.html

Since this helper could help to get consistent error types and messages, I was wondering if we could make a long-running issue to introduce this helper everywhere possible.

I think this could be a good issue for first contributors and short spr

Defining propertynames for non-struct types is not enough to enable tab completion in the REPL, as is being done with Cptr (analytech-solutions/CBinding.jl#77) and eventually with Ptr (JuliaInterop/Clang.jl#316). It appears to be prevented because of the following isstructtype check: https://github.com/JuliaLang/julia/blob/c95448fb988441

Currently many more Python projects like dask and optuna are using Python type hints. With the Python package of xgboost gaining more and more features, we should also adopt mypy as a safe guard against some type errors and for better code documentation.