code: def join_right_in(self, *objs):
          
          if not objs:
              return self.table.c[self.fielda]!=self.table.c[self.fielda]
          else:
              keys = get_objs_columns(objs, self.reference_fieldname)
              return (self.table.c[self.fieldb] == self.reference_class.c[self.reference_fieldname]) & (self.table.c[self.fielda].in_(keys))
docs: Create a join condition, connect B and C