@spec get(BitcoinLib.Key.PublicKey.t(), integer()) ::
  {:ok, BitcoinLib.Key.PublicKey.t()} | {:error, binary()}

Calculates a direct child from a public key based on a given index

examples

Examples

iex> %BitcoinLib.Key.PublicKey{
...>   key: <<0x252C616D91A2488C1FD1F0F172E98F7D1F6E51F8F389B2F8D632A8B490D5F6DA9::264>>,
...>   chain_code: <<0x463223AAC10FB13F291A1BC76BC26003D98DA661CB76DF61E750C139826DEA8B::256>>
...> }
...> |> BitcoinLib.Key.PublicKey.ChildFromIndex.get(0)
{
  :ok,
  %BitcoinLib.Key.PublicKey{
    fingerprint: <<0x9680603F::32>>,
    key: <<0x30204D3503024160E8303C0042930EA92A9D671DE9AA139C1867353F6B6664E59::264>>,
    chain_code: <<0x05AAE71D7C080474EFAAB01FA79E96F4C6CFE243237780B0DF4BC36106228E31::256>>,
    depth: 1,
    index: 0,
    parent_fingerprint: <<0x18C1259::32>>
  }
}