<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_atten(self, idx=0):
 """This function returns the current attenuation from an attenuator at a given index in the instrument. Args: idx: This zero-based index is the identifier for a particular attenuator in an instrument. Raises: Error: The underlying telnet connection to the instrument is not open. Returns: A float that is the current 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 or idx < 0:
            raise IndexError("Attenuator index out of range!", self.path_count,
                             idx)
        atten_val_str = self._telnet_client.cmd("CHAN:%s:ATT?" % (idx + 1))
        atten_val = float(atten_val_str)
        return atten_val