Create a specifier for a continuous contract.

        Parameters
        ----------
        root_symbol_str : str
            The root symbol for the future chain.

        offset : int, optional
            The distance from the primary contract. Default is 0.

        roll_style : str, optional
            How rolls are determined. Default is 'volume'.

        adjustment : str, optional
            Method for adjusting lookback prices between rolls. Options are
            'mul', 'add', and None. Default is 'mul'.

        Returns
        -------
        continuous_future : ContinuousFuture
            The continuous future specifier.

def continuous_future(self,
                          root_symbol_str,
                          offset=0,
                          roll='volume',
                          adjustment='mul'):
        """Create a specifier for a continuous contract.

        Parameters
        ----------
        root_symbol_str : str
            The root symbol for the future chain.

        offset : int, optional
            The distance from the primary contract. Default is 0.

        roll_style : str, optional
            How rolls are determined. Default is 'volume'.

        adjustment : str, optional
            Method for adjusting lookback prices between rolls. Options are
            'mul', 'add', and None. Default is 'mul'.

        Returns
        -------
        continuous_future : ContinuousFuture
            The continuous future specifier.
        """
        return self.asset_finder.create_continuous_future(
            root_symbol_str,
            offset,
            roll,
            adjustment,
        )