def _initForwardOperator(self, **kwargs):
        """Initialize or re-initialize the forward operator.

        Called once in the constructor to force the manager to create the
        necessary forward operator member. Can be recalled if you need to
        changed the mangers own forward operator object. If you want an own
        instance of a valid FOP call createForwardOperator.
        """
        if self._fop is not None:
            fop = self._fop
        else:
            fop = self.createForwardOperator(**kwargs)

        if fop is None:
            pg.critical("It seems that createForwardOperator method "
                        "does not return a valid forward operator.")
        if self.fw is not None:
            self.fw.reset()
            self.fw.setForwardOperator(fop)
        else:
            pg.critical("No inversion framework defined.")