Rotate with just one line

[MasterIphone]

I'm not completely new to Python, but I'm faced with a difficult problem for me.
Previously I wrote parsers and file converters.
Now I need to work with SVG files and I can’t find a solution.
I wrote this code using the Qt5 framework.

# python3 animated_svg.py

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QGraphicsScene, QGraphicsView
from PyQt5.QtCore import Qt, QTimer
from PyQt5.QtSvg import QGraphicsSvgItem

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        # Create scene and view
        self.scene = QGraphicsScene()
        self.view = QGraphicsView(self.scene)
        self.setCentralWidget(self.view)

        # Set screen size
        self.view.setFixedSize(700, 700)

        # Load SVG file with a line
        self.svg_item = QGraphicsSvgItem("two_lines.svg")
        self.scene.addItem(self.svg_item)

        # Find the center of the line
        line_center = self.svg_item.boundingRect().center()

        # Set the rotation origin point to the center of the line
        self.svg_item.setTransformOriginPoint(line_center)

        # Create initial parameters for line rotation
        self.angle = 0  # Initial rotation angle
        self.direction = 1  # Rotation direction: 1 - right, -1 - left

        # Create a timer for animation
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.rotateLine)
        self.timer.start(50)  # Interval in milliseconds

    def rotateLine(self):
        # Increase or decrease the rotation angle
        self.angle += self.direction * 1  # Change the angle by 1 degree

        # Check if we have reached the extreme angle values
        if self.angle >= 45:
            self.angle = 45
            self.direction = -1  # Change direction to left
        elif self.angle <= -45:
            self.angle = -45
            self.direction = 1  # Change direction to right

        # Rotate the line
        self.svg_item.setRotation(self.angle)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    mainWindow = MainWindow()
    mainWindow.show()
    sys.exit(app.exec_())

added two_lines.svg as a separate file
its text is like this:

Output:
<svg xmlns="http://www.w3.org/2000/svg">
  <g id="horizontal_line">
    <line x1="25" y1="100" x2="425" y2="100" stroke="black" stroke-width="2" />
  </g>
  <g id="vertical_line">
    <line x1="225" y1="50" x2="225" y2="150" stroke="red" stroke-width="2" />
  </g>
</svg>

After running the code, I just see the rotation of two lines, although I planned to rotate only one line with id="horizontal_line"

I'll ask the community for help on how to do this.
Perhaps you need to change the text of the SVG file itself and also change the code of the main file.
I'd be grateful for any hints.