def add(self, defn):
        """Adds the given Packet Definition to this Telemetry Dictionary."""
        if defn.name not in self:
            self[defn.name] = defn
        else:
            msg = "Duplicate packet name '%s'" % defn.name
            log.error(msg)
            raise util.YAMLError(msg)
Adds the given Packet Definition to this Telemetry Dictionary.