def register(self, new_formulas, *args, **kwargs):
        """
        Register formula and meta data.

        * ``islinear`` - ``True`` if formula is linear, ``False`` if non-linear.
        * ``args`` - position of arguments
        * ``units`` - units of returns and arguments as pair of tuples
        * ``isconstant`` - constant arguments not included in covariance

        :param new_formulas: new formulas to add to registry.
        """
        kwargs.update(zip(self.meta_names, args))
        # call super method, meta must be passed as kwargs!
        super(FormulaRegistry, self).register(new_formulas, **kwargs)