Temporarily disable plasticity of internal state.

        This function should be implemented by all subclasses so that
        after a call, the output should always be the same for any
        given input pattern, and no call should have any effect that
        persists after restore_plasticity_state() is called.

        By default, simply saves a copy of the 'plastic' parameter to
        an internal stack (so that it can be restored by
        restore_plasticity_state()), and then sets the plastic
        parameter to the given value (True or False).

def override_plasticity_state(self, new_plasticity_state):
        """
        Temporarily disable plasticity of internal state.

        This function should be implemented by all subclasses so that
        after a call, the output should always be the same for any
        given input pattern, and no call should have any effect that
        persists after restore_plasticity_state() is called.

        By default, simply saves a copy of the 'plastic' parameter to
        an internal stack (so that it can be restored by
        restore_plasticity_state()), and then sets the plastic
        parameter to the given value (True or False).
        """
        self._plasticity_setting_stack.append(self.plastic)
        self.plastic=new_plasticity_state