如何在第一次点击后将可点击的QLineEdit转换为正常的？

from PyQt5.QtWidgets import QApplication, QLineEdit, QWidget, QVBoxLayout
from PyQt5.QtCore import Qt

class MyWidget(QWidget):
    def __init__(self):
        super().__init__()
        self.layout = QVBoxLayout()
        self.line_edit = QLineEdit()
        self.line_edit.setPlaceholderText("Click here")
        self.line_edit.setReadOnly(True)
        self.line_edit.setFrame(False)
        self.line_edit.setFixedHeight(30)
        self.line_edit.setFocusPolicy(Qt.NoFocus)
        self.line_edit.mousePressEvent = self.on_line_edit_clicked
        self.layout.addWidget(self.line_edit)
        self.setLayout(self.layout)

    def on_line_edit_clicked(self, event):
        self.line_edit.setReadOnly(False)
        self.line_edit.setStyleSheet("border: 1px solid black")

if __name__ == "__main__":
    app = QApplication([])
    widget = MyWidget()
    widget.show()
    app.exec_()