Kivy Event 在哪里?

kivy 程序都是都需要继承APP基类

而App类在Libsite-packageskivyapp.py文件定义

from kivy.event import EventDispatcher

class App(EventDispatcher):
  pass

找到Libsite-packageskivyevent.py 里面是这样定义的

import kivy._event
__doc__ = kivy._event.__doc__
EventDispatcher = kivy._event.EventDispatcher
ObjectWithUid = kivy._event.ObjectWithUid
Observable = kivy._event.Observable

又引用了Libsite-packageskivy_event.pxd ， 而pxd文件只是个类似c里的头文件（接口声明）, 真正的代码实现在
Libsite-packageskivy_event.cp36-win32.pyd (pxd描述参考)[https://cloud.tencent.com/developer/news/180987]

那为什么在pycharm 里查看时定义处时为什么会跳转到.PyCharm2018.3systempython_stubs498501734kivy_event.py 文件呢，
答案在这里：
https://stackoverflow.com/questions/24266114/pycharm-what-is-python-stubs

写就是说这个文件时pycahrm为我们根据pyd文件生成的，为方便调试代码, 在.PyCharm2018.3systempython_stubs498501734kivy\_event.py 文件都已经
有详细的说明了：

# encoding: utf-8
# module kivy._event
# from xxxxlibsite-packageskivy\_event.cp36-win32.pyd
# by generator 1.146
"""
Event dispatcher
================

All objects that produce events in Kivy implement the :class:`EventDispatcher`
which provides a consistent interface for registering and manipulating event
handlers.

.. versionchanged:: 1.0.9
    Property discovery and methods have been moved from the
    :class:`~kivy.uix.widget.Widget` to the :class:`EventDispatcher`.
"""