Function initialize 

pub fn initialize(
    program_id: &Pubkey,
    stake_pool: &Pubkey,
    manager: &Pubkey,
    staker: &Pubkey,
    stake_pool_withdraw_authority: &Pubkey,
    validator_list: &Pubkey,
    reserve_stake: &Pubkey,
    pool_mint: &Pubkey,
    manager_pool_account: &Pubkey,
    token_program_id: &Pubkey,
    deposit_authority: Option<Pubkey>,
    fee: Fee,
    withdrawal_fee: Fee,
    deposit_fee: Fee,
    referral_fee: u8,
    max_validators: u32,
) -> Instruction

Creates an Initialize instruction.