def get_parameter(self):
        """Obtain list parameter object from the current widget state.

        :returns: A DefaultSelectParameter from the current state of widget.
        """
        current_index = self.input.currentIndex()
        selected_value = self.input.itemData(current_index, Qt.UserRole)
        if hasattr(selected_value, 'toPyObject'):
            selected_value = selected_value.toPyObject()

        try:
            self._parameter.value = selected_value
        except ValueError:
            err = self.raise_invalid_type_exception()
            raise err

        radio_button_checked_id = self.default_input_button_group.checkedId()
        # No radio button checked, then default value = None
        if radio_button_checked_id == -1:
            self._parameter.default = None
        # The last radio button (custom) is checked, get the value from the
        # line edit
        elif (radio_button_checked_id
              == len(self._parameter.default_values) - 1):
            self._parameter.default_values[radio_button_checked_id] \
                = self.custom_value.value()
            self._parameter.default = self.custom_value.value()
        else:
            self._parameter.default = self._parameter.default_values[
                radio_button_checked_id]

        return self._parameter
Obtain list parameter object from the current widget state.

        :returns: A DefaultSelectParameter from the current state of widget.