code: def get_zonefile_data( self, zonefile_hash, zonefile_dir ):
          
          # check cache
          atlas_zonefile_data = get_atlas_zonefile_data( zonefile_hash, zonefile_dir, check=False )
          if atlas_zonefile_data is not None:
              # check hash
              zfh = get_zonefile_data_hash( atlas_zonefile_data )
              if zfh != zonefile_hash:
                  log.debug("Invalid local zonefile %s" % zonefile_hash )
                  remove_atlas_zonefile_data( zonefile_hash, zonefile_dir )
  
              else:
                  log.debug("Zonefile %s is local" % zonefile_hash)
                  return atlas_zonefile_data
  
          return None
docs: Get a zonefile by hash
          Return the serialized zonefile on success
          Return None on error