code: def loc(lexer: Lexer, start_token: Token) -> Optional[Location]:
      
      if not lexer.no_location:
          end_token = lexer.last_token
          source = lexer.source
          return Location(
              start_token.start, end_token.end, start_token, end_token, source
          )
      return None
docs: Return a location object.
  
      Used to identify the place in the source that created a given parsed object.