code: def _merge_variables(new, cur):
      
      new_added = set([])
      out = []
      for cur_var in cur:
          updated = False
          for new_var in new:
              if get_base_id(new_var["id"]) == get_base_id(cur_var["id"]):
                  out.append(new_var)
                  new_added.add(new_var["id"])
                  updated = True
                  break
          if not updated:
              out.append(cur_var)
      for new_var in new:
          if new_var["id"] not in new_added:
              out.append(new_var)
      return out
docs: Add any new variables to the world representation in cur.
  
      Replaces any variables adjusted by previous steps.