code: def lookup_hostname(self, ip):
  		
  		res = self.lookup_by_lease(ip=ip)
  		if "client-hostname" not in res:
  			raise OmapiErrorAttributeNotFound()
  		return res["client-hostname"].decode('utf-8')
docs: Look up a lease object with given ip address and return the associated client hostname.
  
  		@type ip: str
  		@rtype: str or None
  		@raises ValueError:
  		@raises OmapiError:
  		@raises OmapiErrorNotFound: if no lease object with the given ip address could be found
  		@raises OmapiErrorAttributeNotFound: if lease could be found, but objects lacks a hostname
  		@raises socket.error: