code: def convert_schema(self, nuc_tuple, inner_sat_tuples, outer_sat_tuples):
          
          nuc_tree, nuc_pos = nuc_tuple
          sat_tuples = inner_sat_tuples + outer_sat_tuples
          last_sat_tuple_pos = len(sat_tuples)-1
  
          for i, (sat_tree, sat_pos) in enumerate(sat_tuples):
              relname = self.get_relname(sat_tree.root_id)
              if sat_pos < nuc_pos:
                  ordered_trees = [sat_tree, nuc_tree]
              else:
                  ordered_trees = [nuc_tree, sat_tree]
  
              if i == last_sat_tuple_pos:
                  nuc_tree = t(relname, ordered_trees, debug=self.debug, root_id=nuc_tree.root_id)
              else:
                  nuc_tree = t('N', [(relname, ordered_trees)], debug=self.debug, root_id=nuc_tree.root_id)
          return nuc_tree
docs: subtrees are represented as (tree, linear tree position) tuples.
  
          returns relation as root node.