Returns the TableItem instance at row, column cordinates

        Args:
            row (int): zero based index
            column (int): zero based index

def item_at(self, row, column):
        """Returns the TableItem instance at row, column cordinates

        Args:
            row (int): zero based index
            column (int): zero based index
        """
        return self.children[str(row)].children[str(column)]