code: def cares_about(self, delta):
          
          if (self.entity_id and delta.get_id() and
                  not re.match(self.entity_id, str(delta.get_id()))):
              return False
  
          if self.entity_type and self.entity_type != delta.entity:
              return False
  
          if self.action and self.action != delta.type:
              return False
  
          if self.predicate and not self.predicate(delta):
              return False
  
          return True
docs: Return True if this observer "cares about" (i.e. wants to be
          called) for a this delta.