from PyQt5.Qsci import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
import sys

class MainWindow(QMainWindow):
    
    def __init__(self):
        super().__init__()
        tabs = QTabWidget(self)
        
        main_groupbox = QGroupBox(self)
        main_groupbox_layout = QVBoxLayout(main_groupbox)
        main_groupbox_layout.addWidget(tabs)
        main_groupbox.setLayout(main_groupbox_layout)
        #Add the splitters combined in the groupbox to the main form
        self.setCentralWidget(main_groupbox)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    print(app.exec_())