code: def p_file_chk_sum(self, f_term, predicate):
          
          try:
              for _s, _p, checksum in self.graph.triples((f_term, predicate, None)):
                  for _, _, value in self.graph.triples((checksum, self.spdx_namespace['checksumValue'], None)):
                      self.builder.set_file_chksum(self.doc, six.text_type(value))
          except CardinalityError:
              self.more_than_one_error('File checksum')
docs: Sets file checksum. Assumes SHA1 algorithm without checking.