How can I connect a change in QAbstractTableModel to trigger a function

I use QTableView to display a QAbstractTableModel. I edited the QAbstractTableModel so that I can edit the cells, when displayed.

The editing in the window works perfectly, but I want to connect the data change to trigger a function, that takes the new data from the QAbstractTableModel and updates a bar chart.

An example code for the table (without the bar chart) looks like this:

import pandas as pd
import sys
from PyQt5.QtWidgets import QApplication, QTableView, QMainWindow
from PyQt5.QtCore import Qt, QAbstractTableModel


class TableModel(QAbstractTableModel):
    def __init__(self, data):
        super().__init__()
        self._data = data

    def data(self, index, role):
        if role == Qt.DisplayRole:
            # See below for the nested-list data structure.
            # .row() indexes into the outer list,
            # .column() indexes into the sub-list

            return self._data.iloc[index.row(), index.column()]

    def rowCount(self, index):
        # The length of the outer list.
        return self._data.shape[0]

    def columnCount(self, index):
        # The following takes the first sub-list, and returns
        # the length (only works if all rows are an equal length)
        return self._data.shape[1]

    def data(self, index, role=Qt.DisplayRole):
        if index.isValid():
            if role == Qt.DisplayRole or role == Qt.EditRole:
                value = self._data.iloc[index.row(), index.column()]
                return str(value)

    def setData(self, index, value, role):
        if role == Qt.EditRole:
            self._data.iloc[index.row(), index.column()] = value
            return True
        return False

    def headerData(self, col, orientation, role):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            return self._data.columns[col]

    def flags(self, index):
        return Qt.ItemIsSelectable | Qt.ItemIsEnabled | Qt.ItemIsEditable



class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.table = QTableView()

        data = pd.DataFrame([[1, 9, 2], [1, 0, -1], [3, 5, 2], [3, 3, 2], [5, 8, 9],], columns=["A", "B", "C"])

        self.model = TableModel(data)
        self.table.setModel(self.model)

        self.setCentralWidget(self.table)
        self.model.dataChanged.connect(self.update_cells)

    def update_cells(self):
        data = []
        for row in range(self.model.rowCount(self)):
            data.append([])
            for column in range(self.model.columnCount(self)):
                index = self.model.index(row, column)
                # We suppose data are strings
                data[row].append(str(self.model.data(index)))

        data = pd.DataFrame(data, columns=["A", "B", "C"])

app = QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec_()

No error occurs, just nothing happens.