code: async def grant_model(self, username, model_uuid, acl='read'):
          
          model_facade = client.ModelManagerFacade.from_connection(
              self.connection())
          user = tag.user(username)
          model = tag.model(model_uuid)
          changes = client.ModifyModelAccess(acl, 'grant', model, user)
          return await model_facade.ModifyModelAccess([changes])
docs: Grant a user access to a model. Note that if the user
          already has higher permissions than the provided ACL,
          this will do nothing (see revoke_model for a way to remove
          permissions).
  
          :param str username: Username
          :param str model_uuid: The UUID of the model to change.
          :param str acl: Access control ('read, 'write' or 'admin')