Creates :py:class:viz.BaseViz object from the url_params_multidict.

        :return: object of the 'viz_type' type that is taken from the
            url_params_multidict or self.params.
        :rtype: :py:class:viz.BaseViz

def get_viz(self, force=False):
        """Creates :py:class:viz.BaseViz object from the url_params_multidict.

        :return: object of the 'viz_type' type that is taken from the
            url_params_multidict or self.params.
        :rtype: :py:class:viz.BaseViz
        """
        slice_params = json.loads(self.params)
        slice_params['slice_id'] = self.id
        slice_params['json'] = 'false'
        slice_params['slice_name'] = self.slice_name
        slice_params['viz_type'] = self.viz_type if self.viz_type else 'table'

        return viz_types[slice_params.get('viz_type')](
            self.datasource,
            form_data=slice_params,
            force=force,
        )