Function check_row_width 

pub fn check_row_width(
    row: &Row<'_>,
    width: &mut Option<usize>,
    n_columns: usize,
    idx: usize,
) -> Result<(), PolarsError>

Available on crate features object or rows only.

Every row must have the same width as the first, which can be narrower than the schema (the missing columns are filled with nulls) but not wider, as the extra values would otherwise be silently dropped.