def METHOD_NAME(self, abs_key, system, kwargs, vector=None):
    """
    Use this approximation scheme to approximate the derivative d(of)/d(wrt).
    Parameters
    ----------
    abs_key : tuple(str,str)
        Absolute name pairing of (of, wrt) for the derivative.
    system : System
        Containing System.
    kwargs : dict
        Additional keyword arguments, to be interpreted by sub-classes.
    vector : ndarray or None
        Direction for difference when using directional derivatives.
    """
    options = self.DEFAULT_OPTIONS.copy()
    options.update(kwargs)
    options['vector'] = vector
    wrt = abs_key[1]
    if wrt in self._wrt_meta:
        self._wrt_meta[wrt].update(options)
    else:
        self._wrt_meta[wrt] = options
    self._reset()  # force later regen of approx_groups