def update_changes_after_row_delete(self, row_num):
        """
        Update self.changes so that row numbers for edited rows are still correct.
        I.e., if row 4 was edited and then row 2 was deleted, row 4 becomes row 3.
        This function updates self.changes to reflect that.
        """
        if row_num in self.changes.copy():
            self.changes.remove(row_num)
        updated_rows = []
        for changed_row in self.changes:
            if changed_row == -1:
                updated_rows.append(-1)
            if changed_row > row_num:
                updated_rows.append(changed_row - 1)
            if changed_row < row_num:
                updated_rows.append(changed_row)
        self.changes = set(updated_rows)
Update self.changes so that row numbers for edited rows are still correct.
        I.e., if row 4 was edited and then row 2 was deleted, row 4 becomes row 3.
        This function updates self.changes to reflect that.