Adding Text to the plot area

[Protomolekule]

I'm trying to a add formated Text (Font, size,color) to finplot. I want to show symbol information in gray, big letters. (Maybe an image too, but thats future...) Unfortunally the implemented fplt.add_text does not take any format, either as Font nor as html. So I've tried to set text over ax. But I didn't find the right way. Here is my function which I added to my class:

class FP23a (QGraphicsView):
signal_trigger = pyqtSignal()
def init(self, df, title, duration=None, db=None, parent=None, instruments={}):
super (QGraphicsView, self).init (parent)
# Set Plot
self.fplt_widget = self.plotwid () # Erstelle Widget mit Plots und Daten
ax = self.ax_a

    def set_centertext(self, text):
        print("-> set_centertext")

        # get the visibible area
        x0, x1, y0, y1, cnt = self.ax_a.vb.datasrc.hilo (self.ax_a.vb.targetRect ().left (), self.ax_a.vb.targetRect ().right ())
        print(" x0, x1, y0, y1, cnt:",  x0, x1, y0, y1, cnt)
        x_center = int(x0 + (x1 - x0) / 2)
        y_center = int(y1 + (y0 - y1) / 2)

        # Add formatted text
        text_item = QGraphicsTextItem ()
        text_item.setHtml ('<span style="color: red; font-size: 24pt;">%s</span>'%text)
        print("Center: ", x_center, y_center)
        text_item.setPos (x_center, y_center)  # Adjust position as needed

        self.ax_a.vb.scene().addItem(text_item) # not working
        self.ax_a.scene ().addItem (text_item) # also not working

        text_item = pg.TextItem (html='<font size="24" face="Arial">Center Text</font>')
        text_item.setPos (x_center, y_center)
        self.ax_a.scene ().addItem (text_item) # also not working

        label = QLabel("my text")
        label.setFont(QFont('Arial', 20))
        self.layout.addWidget(label)  # Adds label below the plot

I've no idea how this will work. Can someone put in the right direction. I'm sure that this is possible