Function btck_block_get_transaction_at 

pub unsafe extern "C" fn btck_block_get_transaction_at(
    block: *const btck_Block,
    transaction_index: usize,
) -> *const btck_Transaction

@brief Get the transaction at the provided index. The returned transaction is not owned and depends on the lifetime of the block.

@param[in] block Non-null. @param[in] transaction_index The index of the transaction to be retrieved. @return The transaction.