How can I get the parent Resource from RelationManager class?

Hi.
I'm having a

UserResource

UserResource

class, which has the

ContactRelationManager

ContactRelationManager

.

In the Create/Edit/List pages of the

UserResource

UserResource

, I can use method like:

self::getResource()

self::getResource()

to point to the

UserResource

UserResource

class.
So, from the

ContactRelationManager

ContactRelationManager

class, how can I get the full path of the

UserResource

UserResource

class?

Thanks.