PySide6: fail to load "jpg" format in QPixmap - pyqt

Question

I'm trying to load "jpg" picture on the QLabel in PySide6. So I used this:
mypic = QPixmap()
mypic.load("./test.jpg")
self.ui.mylabel.setPixmap(QPixmap(mypic))
However, I found there is empty in mylabel. When I debug in this program, I found that my pic is null (even after it loads the image file).
So I wonder if the jpg is not automatically supported in PySide6.
As I checked the documention of PySide6, it illustrates that the default supporting image formats include "jpg".
enter image description here
As I print the supportedImageFormats using:
print(QtGui.QImageReader.supportedImageFormats())
It returns with this:
[PySide6.QtCore.QByteArray(b'bmp'), PySide6.QtCore.QByteArray(b'pbm'), PySide6.QtCore.QByteArray(b'pgm'), PySide6.QtCore.QByteArray(b'png'), PySide6.QtCore.QByteArray(b'ppm'), PySide6.QtCore.QByteArray(b'xbm'), PySide6.QtCore.QByteArray(b'xpm')]
I found it does not include the "jpg" format by default!
Then I searched a lot of solutions, I found that this can solve my problem: add one line of code to introduce the "imageformats" plugins in PySide6 folder.
app.addLibraryPath(os.path.join(os.path.dirname(QtCore.__file__), "plugins"))
Here I printed the os.path.dirname(QtCore.__file__), and found it was my PySide6 folder.
I checked the plugins folder, and found the inner imageformats folder, and found these dlls:
enter image description here
It seems that the jpg format is supported here. So when I add the plugin path, it can solve my problem. But it still confuses me that why I should add the plugin path (The official documentation implies that this format is supported by default!).
I wonder if there is a more convincing solution because adding one line of code in my program every time seems clumsy. Or if I left out something. I sincerely want to get your help. Thank you!