def _kwargs(self):
        """Returns a list of ``[name, value]`` lists describing the parameters
        of this aggregation instance.

        Returns:
            a list of ``[name, value]`` lists
        """
        return [
            ["field_or_expr", self._field_name],
            ["expr", self._expr],
            ["safe", self._safe],
        ]
Returns a list of ``[name, value]`` lists describing the parameters
        of this aggregation instance.

        Returns:
            a list of ``[name, value]`` lists
        
fiftyone/core/aggregations.py