Why is widget positioning not working in pyQt?

Question

PyQt

There is this code:

import sys
from PySide6.QtGui import *
from PySide6.QtWidgets import *
from PySide6.QtSvgWidgets import *
from PySide6.QtSvg import *
from PySide6 import QtCore
class MainWindow(QMainWindow):


   def mousePressEvent(self, event):
    if event.button() == Qt.LeftButton:
        self.moveFlag = True
        self.movePosition = event.globalPos() - self.pos()
        event.accept()


   def mouseMoveEvent(self, event):
    if Qt.LeftButton and self.moveFlag:
        if self.movePosition.y() <= 50:
            self.move(event.globalPos() - self.movePosition)
        event.accept()


   def mouseReleaseEvent(self, event):
    self.moveFlag = False


   def __init__(self):
    super().__init__()
    
    self.setAttribute(QtCore.Qt.WA_TranslucentBackground)
    self.setWindowFlags(QtCore.Qt.FramelessWindowHint)
    self.resize(720,500)

    self.bg = QFrame()
    self.bg.setStyleSheet("background-color: #e2e6e9; border: none;")
    self.grid = QGridLayout(self.bg)
    self.setCentralWidget(self.bg)

    self.grid.setSpacing(0)
    self.setLayout(self.grid)

    self.svg_widget = QSvgWidget("main.svg")
    self.get_size = QSvgRenderer("main.svg")
    self.svg_widget.setFixedSize(self.get_size.defaultSize())

    
    self.grid.addWidget(self.svg_widget, 0,0)
    
    self.show()

def createApp():    
   app = QApplication(sys.argv)
   window = MainWindow()
   sys.exit(app.exec())

createApp()

By all logic, it should display my svg file in the upper left corner (or I did not understand something), but the result is this: