code: async def add_member(self, db, user):
          ''' Adds a new user to the list of room members, if memeber doesn't exist already '''
  
          # use model's pk as query
          query = {self.primary_key: self.pk}
          # push review
          result = await db[self.get_collection_name()].update_one(
              filter=query,
              update={'$addToSet': {'members': DBRefField(User).to_python(user)}},
          )
          return resulync def add_member(self, db, user):
          ''' Adds a new user to the list of room members, if memeber doesn't exist already '''
  
          # use model's pk as query
          query = {self.primary_key: self.pk}
          # push review
          result = await db[self.get_collection_name()].update_one(
              filter=query,
              update={'$addToSet': {'members': DBRefField(User).to_python(user)}},
          )
          return result
docs: Adds a new user to the list of room members, if memeber doesn't exist already