Inserer graphique dans interface qt5

Bonjour,
je ne comprend pas pourquoi mon graphique ne s'affiche pas dans ma fenetre alors que les boutons s'affiche dans la fenêtre. Je suis débutant en python merci pour vos reponse.
Le graphique est initialiser avec PyQtgraph. Qaund j execute mon code 2 fenetre s'oubre le graphique et une autre fenetre avec le bouton.

from PyQt5.QtWidgets import  QListWidget, QLabel,  QPushButton
import pyqtgraph as pg
from collections import deque
from pyqtgraph.Qt import QtGui
import numpy as np
import sys
from PyQt5.QtWidgets import QMainWindow, QPlainTextEdit
from PyQt5 import QtWidgets

class Window(QMainWindow):

global mess
def __init__(self):
super().__init__()

self.setWindowTitle("fenetre1")
self.setGeometry(300,500,800,750)

self.MyUI()



def MyUI(self):






g=self.Graph() #graphique appeler dans la fonction MyUI

button = QPushButton("sauvegarder", self)#initialisation du bouton
button.clicked.connect(self.appui_bouton1)
button.setStyleSheet("background-color: yellow;font-size:18px;font-family:Impact;")
button.resize(150,50)
button.move(1100, 100)

button2 = QPushButton("supprimer", self)
button2.clicked.connect(self.appui_bouton2)
button2.setStyleSheet("background-color: red;font-size:18px;font-family:Impact;")
button2.resize(150,50)
button2.move(1100, 180)

button3 = QPushButton("suivant", self)
button3.clicked.connect(self.appui_bouton3)
button3.setStyleSheet("background-color: green;font-size:18px;font-family:Impact;")
button3.resize(150,50)
button3.move(1100, 260)






def appui_bouton1(self):
print("le fichier a été sauvergarder")


def appui_bouton2(self):
print("le fichier a été supprimer")
#os.remove("graph2.png")


def appui_bouton3(self):
print("suivant")




def Graph(self):

self.dat = deque()
self.maxLen = 50#max number of data points to show on graph
self.app = QtGui.QApplication([])
self.win = pg.GraphicsWindow()
self.win.setWindowTitle('graph1')

self.label = pg.LabelItem(justify='right')
self.win.addItem(self.label)

self.p1 = self.win.addPlot(row=1, col=0)
self.win.nextRow()

self.region = pg.LinearRegionItem()
self.region.setZValue(10)
self.p1.setAutoVisible(y=True)
#plt.axis([-1,1,-3,3])
self.x=np.linspace(0,23,15000)
self.data1 = np.cos(self.x)
self.p1.showGrid(x=True, y=True)
self.p1.plot(self.data1, pen="y")




def updateRegion(window, viewRange):
rgn = viewRange[0]
self.region.setRegion(rgn)

self.p1.sigRangeChanged.connect(updateRegion)
self.region.setRegion([1000, 2000])


vLine = pg.InfiniteLine(angle=90, movable=False)
hLine = pg.InfiniteLine(angle=0, movable=False)
self.p1.addItem(vLine, ignoreBounds=True)
self.p1.addItem(hLine, ignoreBounds=True)

vb = self.p1.vb



def mouseMoved(evt):
pos = evt[0] ## using signal proxy turns original arguments into a tuple
if self.p1.sceneBoundingRect().contains(pos):
mousePoint = vb.mapSceneToView(pos)
index = int(mousePoint.x())
if index > 0 and index < len(self.data1):
self.label.setText("<span style='font-size: 12pt'><span style='color: yellow'>x=%0.1f, <span style='color: yellow'>y1=%0.1f</span>" % (mousePoint.x(), self.data1[index]))
vLine.setPos(mousePoint.x())
hLine.setPos(mousePoint.y())





proxy = pg.SignalProxy(self.p1.scene().sigMouseMoved, rateLimit=60, slot=mouseMoved)

#QtGui.QApplication.instance().exec_()


if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
mainWin = Window()
mainWin.show()
sys.exit( app.exec_() )
</code>