'Proceed to a given step'

def _set_step(self, step):

    new_tab = (self.tab_widget.currentIndex() + step)
    assert ((new_tab < self.tab_widget.count()) and (new_tab >= 0))
    if (new_tab == (self.tab_widget.count() - 1)):
        try:
            self.table_widget.open_data(self._get_plain_text(), self.text_widget.get_col_sep(), self.text_widget.get_row_sep(), self.text_widget.trnsp_box.isChecked(), self.text_widget.get_skiprows(), self.text_widget.get_comments())
            self.done_btn.setEnabled(True)
            self.done_btn.setDefault(True)
            self.fwd_btn.setEnabled(False)
            self.back_btn.setEnabled(True)
        except (SyntaxError, AssertionError) as error:
            QMessageBox.critical(self, _('Import    wizard'), (_('<b>Unable    to    proceed    to    next    step</b><br><br>Please    check    your    entries.<br><br>Error    message:<br>%s') % str(error)))
            return
    elif (new_tab == 0):
        self.done_btn.setEnabled(False)
        self.fwd_btn.setEnabled(True)
        self.back_btn.setEnabled(False)
    self._focus_tab(new_tab)
