Can the where constraint also be an Object?

[SeloSlav]

public Builder where(String key, String value) {
            this.baseQuery.whereKey = key;
            this.baseQuery.whereValue = value;
            return this;
        }

For example, I'm looking for Message objects where the field conversationObject (Pointer<Conversation>) matches a particular object, i.e. Conservation conservation = new Conversation();

final Subscription sub = new BaseQuery.Builder("Message")
                                .where("conversationObject", conservation)
                                // .addField("field_to_be_returned")
                                .build()
                                .subscribe();

Why can't I filter by objects instead of just strings?