code: def generate(self):
          
          t = (self.context.identifier, RDF.type, META.Provenance)
          if t not in self.context.graph:
              self.context.graph.add(t)
          for name, value in self.data.items():
              pat = (self.context.identifier, META[name], None)
              if pat in self.context.graph:
                  self.context.graph.remove(pat)
              self.context.graph.add((pat[0], META[name], Literal(value)))
docs: Add provenance info to the context graph.