def set_atten(self, idx, value):
        """Sets the attenuation value for a particular signal path.

        Args:
            idx: Zero-based index int which is the identifier for a particular
                signal path in an instrument. For instruments that only has one
                channel, this is ignored by the device.
            value: A float that is the attenuation value to set.

        Raises:
            Error: The underlying telnet connection to the instrument is not
                open.
            IndexError: The index of the attenuator is greater than the maximum
                index of the underlying instrument.
            ValueError: The requested set value is greater than the maximum
                attenuation value.
        """
        if not self.is_open:
            raise attenuator.Error(
                "Connection to attenuator at %s is not open!" %
                self._telnet_client.host)
        if idx + 1 > self.path_count:
            raise IndexError("Attenuator index out of range!", self.path_count,
                             idx)
        if value > self.max_atten:
            raise ValueError("Attenuator value out of range!", self.max_atten,
                             value)
        # The actual device uses one-based index for channel numbers.
        self._telnet_client.cmd("CHAN:%s:SETATT:%s" % (idx + 1, value))
Sets the attenuation value for a particular signal path.

        Args:
            idx: Zero-based index int which is the identifier for a particular
                signal path in an instrument. For instruments that only has one
                channel, this is ignored by the device.
            value: A float that is the attenuation value to set.

        Raises:
            Error: The underlying telnet connection to the instrument is not
                open.
            IndexError: The index of the attenuator is greater than the maximum
                index of the underlying instrument.
            ValueError: The requested set value is greater than the maximum
                attenuation value.