Function datetime_ranges 

pub fn datetime_ranges(
    start: Option<Expr>,
    end: Option<Expr>,
    interval: Option<Duration>,
    num_samples: Option<Expr>,
    closed: ClosedWindow,
    time_unit: Option<TimeUnit>,
    time_zone: Option<TimeZone>,
) -> Result<Expr, PolarsError>

Create a column of datetime ranges from start, end, interval, and num_samples expressions.