Function ST_GeometryN 

pub fn ST_GeometryN<gc, n>(
    gc: gc,
    n: n,
) -> ST_GeometryN<<gc as AsExpression<GeometryCollection>>::Expression, <n as AsExpression<Integer>>::Expression>
where
    gc: AsExpression<GeometryCollection>,
    n: AsExpression<Integer>,

Represents the MySQL ST_GeometryN function