// convert to type erased ArrayRef
// all arrays implement this
fn to_arrow(&self) -> DaftResult<ArrayRef>;
// convert to a concrete type which varies for each array type
// such as DataArray<Int8Type> -> arrow::array::Int8Array
// most arrays implement this, but not all of them. 
// this is also true for the original `as_arrow` (now `as_arrow2`) that this is intended to replace.
fn as_arrow(&self) -> DaftResult<Self::ArrowOutput>

// this is also implemented for all arrays. 
fn from_arrow<F: Into<Arc<Field>>>(field: F, array: ArrayRef) -> DaftResult<Self>;