src/Extension/MemberExtension.php
public static function get_by_identifier($idvalue)
    {
        return Member::get()->filter(
            Member::config()->unique_identifier_field,
            $idvalue
        )->first();
    }
public static function get_by_identifier($idvalue)
    {
        return Member::get()->filter(
            Member::config()->unique_identifier_field,
            $idvalue
        )->first();
    }
Get member by unique field.

@return Member|null