code: def to_sql(self, instring, schema, use_bag_semantics=False):
          
          root_list = self.to_syntax_tree(instring, schema)
          return sql_translator.translate(root_list, use_bag_semantics)
docs: Translate a relational algebra string into a SQL string.
  
          :param instring: a relational algebra string to translate
          :param schema: a mapping of relation names to their attributes
          :param use_bag_semantics: flag for using relational algebra bag semantics
          :return: a SQL translation string