custom<'a, 'b> (key: string) (typeName: string) (tryParse: string -> 'a option) (innerParser: Parser<('a option -> 'b)>) : Parser<'b>
int<'a> (key: string) (innerParser: Parser<(int option -> 'a)>) : Parser<'a>
string<'a> (key: string) (innerParser: Parser<(string option -> 'a)>) : Parser<'a>