HAS_ONE = Mongoid::Association::Referenced::HasOne
        HAS_MANY = Mongoid::Association::Referenced::HasMany
        HAS_AND_BELONGS_TO_MANY = Mongoid::Association::Referenced::HasAndBelongsToMany
        BELONGS_TO = Mongoid::Association::Referenced::BelongsTo
        EMBEDS_ONE = Mongoid::Association::Embedded::EmbedsOne