Check if this instance can model and/or can invert

def _check_state(self):
        """Check if this instance can model and/or can invert
        """
        if(self.grid is not None and
           self.configs.configs is not None and
           self.assignments['forward_model'] is not None):
            self.can_model = True

        if(self.grid is not None and
           self.assignments['measurements'] is not None):
            self.can_invert = True