now,`hostname_to_ip` only can resolve `ipv4`,Therefore, a method is provided to parse ipv4 or ipv6 based on parameters。 when `_heartbeat` call `hostname_to_ip`,Resolve to ipv4 or ipv6, determined by `BackendOptions.is_bind_ipv6` Decision Additionally, a method is provided to first attempt to parse the host into ipv4, and then try ipv6 if it fails