code: def eventFilter(self, widget, event):
          
          if event.type() == QEvent.MouseButtonPress:
              if event.button() == Qt.LeftButton:
                  self.sig_canvas_clicked.emit(self)
          return super(FigureThumbnail, self).eventFilter(widget, event)
docs: A filter that is used to send a signal when the figure canvas is
          clicked.