Support basic math NumPy functions

[Raphael-CV]

Support basic math NumPy functions

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[Raphael-CV]

@googlebot I signed it.

[odashi]

Thanks! It looks the title of this pull request seems to be "support NumPy functions" because this change does really not support the whole stuff in NumPy.

[odashi]

@Raphael-CV If you have several ideas to implement, is it possible to propose separate pull requests for each idea? Mixed pull requests are sometimes difficult to maintain and I think we need to focus on the feature about NumPy functions in this specific pull request.

[Raphael-CV]

It seems indeed that it is a better idea. I revert the last commits and will propose several pull requests.

[odashi]

@Raphael-CV Thanks a lot!