code: def bottomup(cls):
          
          return tuple(unique_everseen(r for r in cls._instances.values() if r.direction=='bottomup'))
docs: Get all bottomup `Relationship` instances.
  
          Example:
  
              >>> from pronto import Relationship
              >>> for r in Relationship.bottomup():
              ...    print(r)
              Relationship('is_a')
              Relationship('part_of')
              Relationship('develops_from')