Type hints and type check

Type hints is a modern Python way to provide type information (see typing mypy). PR https://github.com/tarantool/tarantool-python/pull/264 is the first one to potentially use type hints, but it would be nice to have it anywhere.

Type asserts is a more tricky question. For now there are some minor type checks and asserts in connector. Some may also be implemented in PR #264. But it is a big question if they should be use. It seems that there are both adepts of using (since it is a convenient concept) and forbidding to use (since it contradicts Python duck typing principle) it. For example, see this StackOverflow thread. One way or another, it would be good to at least have a consistency on this question.

Since now package is fully documented, it should be easy to implement type hints and asserts after one decide what approach we should stick to. But choosing the approach is the question.

まず PR #264 と、既存の connector の型チェックおよび asserts を読み、次にパッケージのドキュメントと、リンクされている typing および mypy のリファレンスを確認してください。この Issue では、最初に型ヒントを追加するかどうか、また実行時の型チェックまたは asserts をどの程度一貫して使用するかを決める必要があります。合意した方針がパッケージ全体に適用されれば完了です。