Plotting time series data with PyQtGraph

Hello I have a serious issue here and I can’t find a solution any where else. I try to plot time series data on my PyqtGraph embedded to QT designer.

the only tutos I found with time series plot pyqtgraph are as follow : python - How can I use DateAxisItem of PyQtGraph? - Stack Overflow

my question is how do we replace the

graph = pg.PlotWidget(axisItems = {'bottom': date_axis})


self.graphWidget = pg.PlotWidget(axisItems = {'bottom': date_axis})

The first works but the second does not. is it possible to show how you would add a timeseries on your example it would be SUPERUSEFUL because there is no any on google.