code: def convert_relational(relational):
      
      rel = relational.rel_op
      if rel in ['==', '>=', '>']:
          return relational.lhs-relational.rhs
      elif rel in ['<=', '<']:
          return relational.rhs-relational.lhs
      else:
          raise Exception("The relational operation ' + rel + ' is not "
                          "implemented!")
docs: Convert all inequalities to >=0 form.