Parsed documentation:
View on GitHub
Validates the attribute is not a member of the given enumerable.

This validator has the same semantics as calling
`not Enum.member?/2` with the given enumerable and value.

Nil values are not matched against (skipped).

## Options

* `:message` - defaults to "is reserved"

## Examples

    validate user,
      username: not_member_of(~w(admin superuser))

    validate user,
      password: not_member_of([user.username,],
                              message: "cannot be the same as username or first name")
Please help! Open an issue on GitHub if this assessment is incorrect.