code: def get_subdomain_history_neighbors(self, cursor, subdomain_rec):
          
          # what's the subdomain's immediate prior history?
          hist = self.subdomain_db.get_subdomain_history(subdomain_rec.get_fqn(), include_unaccepted=True, start_sequence=subdomain_rec.n-1, end_sequence=subdomain_rec.n, cur=cursor)
          hist.sort(lambda h1, h2: -1 if h1.n < h2.n or (h1.n == h2.n and h1.parent_zonefile_index < h2.parent_zonefile_index) \
                                   else 0 if h1.n == h2.n and h1.parent_zonefile_index == h2.parent_zonefile_index \
                                   else 1)
  
          # what's the subdomain's current and immediate future?
          fut = self.subdomain_db.get_subdomain_history(subdomain_rec.get_fqn(), include_unaccepted=True, start_sequence=subdomain_rec.n, end_sequence=subdomain_rec.n+2, cur=cursor)
          fut.sort(lambda h1, h2: -1 if h1.n < h2.n or (h1.n == h2.n and h1.parent_zonefile_index < h2.parent_zonefile_index) \
                                   else 0 if h1.n == h2.n and h1.parent_zonefile_index == h2.parent_zonefile_index \
                                   else 1)
  
          # extract the current (conflicting) records from the future
          cur = []
          tmp_fut = []
          for f in fut:
              if f.n == subdomain_rec.n:
                  cur.append(f)
              else:
                  tmp_fut.append(f)
  
          fut = tmp_fut
  
          ret = {'prev': hist, 'cur': cur, 'fut': fut}
          return ret
docs: Given a subdomain record, get its neighbors.
          I.e. get all of the subdomain records with the previous sequence number,
          and get all of the subdomain records with the next sequence number
          Returns {'prev': [...blockchain order...], 'cur': [...blockchain order...], 'fut': [...blockchain order...]}