Reorganized import statements.

sohstationviewer.py

 import sys
+
 from PySide2 import QtWidgets
+
 from sohstationviewer.view.mainwindow import MainWindow
 
 

sohstationviewer/view/calendardialog.py

 from PySide2 import QtWidgets
+
 from sohstationviewer.view.ui.calendar_ui import Ui_CalendarDialog
 
 

sohstationviewer/view/mainwindow.py

 import pathlib
+
 from PySide2 import QtCore, QtGui, QtWidgets
+
 from sohstationviewer.view.ui.main_ui import Ui_MainWindow
 from sohstationviewer.view.calendardialog import CalendarDialog
 from sohstationviewer.view.calendarwidget import CalendarWidget