code: def _resetWidgets(self):
          
          self._filenameLineEdit.setText('')
          self._encodingComboBox.setCurrentIndex(0)
          self._delimiterBox.reset()
          self._headerCheckBox.setChecked(False)
          self._statusBar.showMessage('')
          self._previewTableView.setModel(None)
          self._datatypeTableView.setModel(None)
docs: Resets all widgets of this dialog to its inital state.