human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Year, Entrant, Chassis, Engine, Points
###Question: What is the entrant of a chassis maserati 250f, also has 6 points and older than year 1957?
gpt
SELECT Entrant FROM table WHERE Chassis = maserati 250f AND Points = 6 AND Year < 1957