你好，我正在用kivy和python开发移动的应用程序。一切都很好，直到我想用sqlite3。下面是我的目录结构：

application
├───main.py
├───core
│   └───__pycache__
|   ├───calendar_screen.py
|   ├───children.py
|   ├───menu.py
|   ├───screen_manager.py
|   ├───settings.py
|   └───vaccination.py
├───database
|   ├───vaccination_calendar.db
|   ├───vaccination_calendar.py
│   └───__pycache__
├───fonts
│   └───static
│       ├───OpenSans
│       ├───OpenSans_Condensed
│       └───OpenSans_SemiCondensed
├───images
│   └───icons
├───layouts
|   ├───calendar.kv
|   ├───children.kv
|   ├───menu.kv
|   ├───screen_manager.kv
|   ├───settings.kv
|   └───vaccination.kv
└───__pycache__

相关代码main.py

from kivymd.app import MDApp

from core.screen_manager import WindowManager

class VaccinationCalendarApp(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "Green"
        return WindowManager()

if __name__ == "__main__":
    VaccinationCalendarApp().run()

屏幕管理器.py

from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager

Builder.load_file("layouts/screen_manager.kv")

class WindowManager(ScreenManager):
    pass

屏幕管理器.kv

#: import Menu core.menu
#: import Calendar core.calendar_screen
#: import Children core.children
#: import Vaccination core.vaccination
#: import Settings core.settings

<WindowManager>:
    Menu:
    Calendar:
    Children:
    Vaccination:
    SettingsScreen:

children.py

from kivy.lang import Builder
from kivy.uix.screenmanager import Screen
from kivymd.uix.list import OneLineAvatarIconListItem, IconLeftWidget
from application.database.vaccination_calendar import get_children

Builder.load_file("layouts/children.kv")

class Children(Screen):
    pass

疫苗接种_日历.py

import sqlite3

def get_children():
    statement = "select * from children"

    with sqlite3.connect("vaccination_calendar.db") as conn:
        cursor = conn.cursor()
        cursor.execute(statement)
        children_list = [{"id": child[0], "name": child[1], "birth_date": child[2], "days_age": child[3]}
                         for child in cursor.fetchall()]
        conn.commit()

    return children_list

在www.example.com中出现这一行之前，一切都很正常children.py：from application.database.vaccination_calendar import get_children.添加这一行之后，我得到了带有追溯功能的AttributeError：

Traceback (most recent call last):
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\application\main.py", line 3, in <module>
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\builder.py", line 305, in load_file
     return self.load_string(data, **kwargs)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\builder.py", line 372, in load_string
     parser = Parser(content=string, filename=fn)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 483, in __init__
     self.parse(content)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 590, in parse
     self.execute_directives()
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 559, in execute_directives
     mod = getattr(mod, part)
 AttributeError: module 'core' has no attribute 'children'

我怀疑这是循环依赖的问题，但我看不出有什么问题。我过去这里的文件是从www.example.com开始的导入顺序main.py。
我尝试通过www.example.com中的方法导入vaccination_calendar.pychildren.py，但之后我收到ModuleNotFoundError，我还尝试导入main.py，在那里它工作正常，但我没有看到任何在儿童屏幕中使用vaccination_calendar.py的想法。