code: def add_role_to_user(self, user, role):
          
          user, role = self._prepare_role_modify_args(user, role)
          result = self.UserRole.select().where(
              self.UserRole.user == user.id,
              self.UserRole.role == role.id,
          )
          if result.count():
              return False
          else:
              self.put(self.UserRole.create(user=user.id, role=role.id))
              return True
docs: Adds a role to a user.
  
          :param user: The user to manipulate
          :param role: The role to add to the user