in crates/core/src/avro_to_arrow/arrow_array_reader.rs [904:916]
fn resolve_fixed(v: &Value, size: usize) -> Option<Vec<u8>> {
let v = if let Value::Union(_, b) = v { b } else { v };
match v {
Value::Fixed(n, bytes) => {
if *n == size {
Some(bytes.clone())
} else {
None
}
}
_ => None,
}
}