code: 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)
docs: Proceed to a given step