Function retrieve 

pub fn retrieve(handle: RequestHandle, out_buffer: &mut [u8]) -> FFIResult<()>

Retrieve the resulting output buffer from a request that is ready.

This should only be called once is_ready on the request is true

Returns

• crate::ErrorCode::Success - if results were successfully retrieved
• crate::ErrorCode::InvalidArguments - if any of the parameters are invalid
• crate::ErrorCode::Unavailable - if the handle is valid but the results are not available yet