Function tract_value_as_bytes 

pub unsafe extern "C" fn tract_value_as_bytes(
    value: *mut TractValue,
    datum_type: *mut DatumType,
    rank: *mut usize,
    shape: *mut *const usize,
    data: *mut *const c_void,
) -> TRACT_RESULT

Inspect part of a value. Except value, all argument pointers can be null if only some specific bits are required.