Return snmp value for the first OID.

def get_first(self):
		"""Return snmp value for the first OID."""
		try: # Nested try..except because of Python 2.4
			self.lock.acquire()
			try:
				return self.get(self.data_idx[0])
			except (IndexError, ValueError):
				return "NONE"
		finally:
			self.lock.release()