IP.is_ipv6

You're seeing just the macro is_ipv6, go back to IP module for more information.

true if the argument is an ipv6 datatype

usable in guards.

iex> IP.is_ipv6({0, 0, 0, 0, 0, 0, 0, 1})
true
iex> IP.is_ipv6(:foo)
false
iex> IP.is_ipv6({0x10000, 0, 0, 0, 0, 0, 0, 1})
false