Improve message if user forgot to call a function

Forgetting to call a method, i.e. missing (), is a somewhat common programming error. Mypy will typically catch this error, but often error messages includes something like "Callable[...]" has no attribute "foo". Since the callable type may be pretty complicated, this can look confusing.

Here are a few ideas that could make this better:

1. Only say Callable object has no attribute "foo" (omit the full callable type).
2. Add a note such as Did you mean ".foo()" (with parentheses)? (needs wordsmithing).
3. In addition to (1), show the signature of the function in a separate note pretty-printed using function definition syntax such as def foo() -> List[X].

ファイルもテストも指定されていません。まず、属性がないと報告された Callable オブジェクトに対する mypy の診断パスを特定し、次に提案された文言とシグネチャ注記の選択肢を比較します。混乱を招く Callable 型がより明確に提示され、回帰テストのカバレッジによって括弧の付け忘れに関する案内が検証されれば完了です。