*
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

В этом случае вам может понадобиться задокументировать, как должно выглядеть это внешнее API: какую *операцию пути* оно должно иметь, какое тело запроса ожидать, какой ответ возвращать и т.д.

## Приложение с обратными вызовами { #an-app-with-callbacks }

Давайте рассмотрим это на примере.

Представьте, что вы разрабатываете приложение, позволяющее создавать счета.

Эти счета будут иметь `id`, `title` (необязательный), `customer` и `total`.

Por ejemplo, el modelo anterior declara un “`object`” JSON (o `dict` en Python) como:

```JSON
{
    "name": "Foo",
    "description": "An optional description",
    "price": 45.2,
    "tax": 3.5
}
```

...dado que `description` y `tax` son opcionales (con un valor por defecto de `None`), este “`object`” JSON también sería válido:

```JSON
{

	type jobKV BatchJobKV
	var tmp jobKV
	err := val.Decode(&tmp)
	if err != nil {
		return err
	}
	*kv = BatchJobKV(tmp)
	kv.line, kv.col = val.Line, val.Column
	return nil
}

// Validate returns an error if key is empty
func (kv BatchJobKV) Validate() error {
	if kv.Key == "" {
		return BatchJobYamlErr{
			line: kv.line,
			col:  kv.col,
			msg:  "key can't be empty",
		}
	}
	return nil
}

	// Verify if region is valid.
	sRegion := cred.scope.region
	// Region is set to be empty, we use whatever was sent by the
	// request and proceed further. This is a work-around to address
	// an important problem for ListBuckets() getting signed with
	// different regions.
	if region == "" {
		region = sRegion
	}
	// Should validate region, only if region is set.
	if !isValidRegion(sRegion, region) {

# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

	errDecommissionNotStarted     = errors.New("decommission is not in progress")
)

func (p *poolMeta) Decommission(idx int, pi poolSpaceInfo) error {
	// Return an error when there is decommission on going - the user needs
	// to explicitly cancel it first in order to restart decommissioning again.
	if p.Pools[idx].Decommission != nil &&
		!p.Pools[idx].Decommission.Complete &&