Function encode_setup 

pub fn encode_setup(
    owners: &[[u8; 20]],
    threshold: u64,
    to: [u8; 20],
    data: &[u8],
    fallback_handler: [u8; 20],
    payment_token: [u8; 20],
    payment: u128,
    payment_receiver: [u8; 20],
) -> Vec<u8> 

ABI-encode setup(address[] calldata _owners, uint256 _threshold, ...).

The initializer called when deploying a new Safe proxy.