def __init__(self, petros, mgrs):
        """Initialize with lists of managers and transformations"""
        self.mgrs = mgrs

        self.fops = [pg.frameworks.PetroModelling(m.fop, p)
                     for p, m in zip(petros, mgrs)]

        super().__init__(fop=pg.frameworks.JointModelling(self.fops))

        # just hold a local copy
        self.dataTrans = pg.trans.TransCumulative()