Function build_unnest_op 

pub fn build_unnest_op(
    array_column: impl Into<String>,
    output_column: impl Into<String>,
    with_ordinality: bool,
) -> NodeOp

Build a NodeOp::Unnest descriptor.

• array_column — the source column that contains the array.
• output_column — the name of the column produced for each element.
• with_ordinality — when true an extra ordinality column (u64) is appended with the 1-based position of each element.