code: def create_checksum_node(self, chksum):
          
          chksum_node = BNode()
          type_triple = (chksum_node, RDF.type, self.spdx_namespace.Checksum)
          self.graph.add(type_triple)
          algorithm_triple = (chksum_node, self.spdx_namespace.algorithm, Literal(chksum.identifier))
          self.graph.add(algorithm_triple)
          value_triple = (chksum_node, self.spdx_namespace.checksumValue, Literal(chksum.value))
          self.graph.add(value_triple)
          return chksum_node
docs: Return a node representing spdx.checksum.