@property<EOL><INDENT>def safe(self):<DEDENT>
return self._safe<EOL>
Whether this channel is 'safe' to use as a noise witness

        Any channel that records part or all of a GW signal as it
        interacts with the interferometer is not safe to use as a noise
        witness

        A safe value of `None` simply indicates that the safety of this
        channel has not been determined

        :type: `bool` or `None`