Function _join_asof_dispatch 

pub fn _join_asof_dispatch(
    left_key: &Series,
    right_key: &Series,
    strategy: AsofStrategy,
    tolerance: Option<AnyValue<'static>>,
    allow_eq: bool,
) -> Result<ChunkedArray<UInt32Type>, PolarsError>

Available on crate feature polars-ops only.