code: def _add_to_ref(self, rec_curr, line):
          
          # Examples of record lines containing ':' include:
          #   id: GO:0000002
          #   name: mitochondrial genome maintenance
          #   namespace: biological_process
          #   def: "The maintenance of ...
          #   is_a: GO:0007005 ! mitochondrion organization
          if line[:4] == "id: ":
              assert not rec_curr.item_id
              item_id = line[4:]
              rec_curr.item_id = item_id
              rec_curr.id = item_id
          elif line[:8] == "alt_id: ":
              rec_curr.alt_ids.add(line[8:])
          elif line[:6] == "name: ":
              assert not rec_curr.name
              rec_curr.name = line[6:]
          elif line[:11] == "namespace: ":
              assert not rec_curr.namespace
              rec_curr.namespace = line[11:]
          elif line[:6] == "is_a: ":
              rec_curr._parents.add(line[6:].split()[0])
          elif line[:13] == "is_obsolete: " and line[13:] == "true":
              rec_curr.is_obsolete = True
          elif self.optobj and ':' in line:
              self.optobj.update_rec(rec_curr, line)
docs: Add new fields to the current reference.