def apply(self, name, foci):
        """ Apply a named transformation to a set of foci.

        If the named transformation doesn't exist, return foci untransformed.
        """
        if name in self.transformations:
            return transform(foci, self.transformations[name])
        else:
            logger.info(
                "No transformation named '%s' found; coordinates left "
                "untransformed." % name)
            return foci