Withdraws gas from the GasBuiltin to handle the success case flow. Returns Some(()) if there is sufficient gas to handle the success case, otherwise returns None.

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Signature

pub extern fn withdraw_gas() -> Option implicits(RangeCheck, GasBuiltin) nopanic;

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Examples

// The success branch is the following lines, the failure branch is the `panic` caused by the
// `unwrap` call.
withdraw_gas().unwrap();

// Direct handling of `withdraw_gas`.
match withdraw_gas() {
    Some(()) => success_case(),
    None => cheap_not_enough_gas_case(),
}