imported group.indexOf not work

[tochy-open]

Describe the bug
After group imported, members return string[]
indexOf function always return -1

To Reproduce
Steps to reproduce the behavior:

const group_origin = new Group([1n, 2n, 3n, 4n, 5n])
const exported = group_origin.export()
console.log('group test', group_origin.members)
console.log(group_origin.indexOf(3n))
console.log(group_origin.indexOf('3'))
console.log(group_origin.indexOf(BigInt('3')))
console.log(group_origin.members.indexOf(3n))
console.log(group_origin.members.indexOf(BigInt('3')))

const group = Group.import(exported)
console.log('group imported', group.members)
console.log(group.indexOf(3n))
console.log(group.indexOf('3'))
console.log(group.indexOf(BigInt('3')))
console.log(group.members.indexOf(3n))
console.log(group.members.indexOf(BigInt('3')))

const converted = group.members.map(id => id.toString())
console.log('members bigint[] to string[]')
console.log(converted.indexOf('3'))

Expected behavior
imported group.indexOf return correct position

Screenshots

[cedoor]

Thanks @tochy-open 🙏🏽 WIP

Re: privacy-scaling-explorations/zk-kit#313