Retrive a quantify modifier, normalized.
        This function would also return a tuple, with the first item a callable,
        and the rest native quantity names

        Parameters
        ----------
        quantity : str
            name of the derived quantity to get

        Returns
        -------
        tuple : (callable, quantity1, quantity2...)

def get_normalized_quantity_modifier(self, quantity):
        """
        Retrive a quantify modifier, normalized.
        This function would also return a tuple, with the first item a callable,
        and the rest native quantity names

        Parameters
        ----------
        quantity : str
            name of the derived quantity to get

        Returns
        -------
        tuple : (callable, quantity1, quantity2...)
        """
        modifier = self._quantity_modifiers.get(quantity, self._default_quantity_modifier)
        if modifier is None:
            return (trivial_callable, quantity)

        if callable(modifier):
            return (modifier, quantity)

        if isinstance(modifier, (tuple, list)) and len(modifier) > 1 and callable(modifier[0]):
            return modifier

        return (trivial_callable, modifier)