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类型注解
***************************

自定义类型
===========================

.. code-block:: python

    from typing import TypeVar

    T = TypeVar('T')  # Can be anything
    A = TypeVar('A', str, bytes)  # Must be str or bytes

可调用参数
==========================

预期特定签名回调函数的框架可以用 Callable[[Arg1Type, Arg2Type], ReturnType] 实现类型提示。

.. code-block:: python

    from collections.abc import Callable

    def feeder(get_next_item: Callable[[], str]) -> None:
        # Body

    def async_query(on_success: Callable[[int], None],
                    on_error: Callable[[int, Exception], None]) -> None:
        # Body