code: def nt_yielder(self, graph, size):
          
          for grp in self.make_batch(size, graph):
              tmpg = Graph()
              # Add statements as list to tmp graph
              tmpg += grp
              yield (len(tmpg), tmpg.serialize(format='nt'))
docs: Yield n sized ntriples for a given graph.
          Used in sending chunks of data to the VIVO
          SPARQL API.