Remove child metric

Hello.
Tried to remove some childs, but got KeyError.

My custom metric (gauge) have some lables and worked fine. But when i needed to delete some childs, i'm stuck:

global statusOK
statusOK = "OK"
global statusNOK
statusNOK = "Fail"

service_login_status_prom = prom.Gauge('service_login_status', 'Check access token availability', ['status', 'dc_name'])
result = str('0')
service_login_status_prom.labels(statusOK, dc_name).set(result)
service_login_status_prom.remove(statusNOK, dc_name)

https://github.com/prometheus/client_python/blob/09fb45953bac018a90e89f0b1e7bcd1d5d81c01b/prometheus_client/metrics.py#L187

Error is -

File "/usr/local/lib/python3.8/site-packages/prometheus_client/metrics.py", line 187, in remove

   del self._metrics[labelvalues]
   KeyError: ('Fail', '11u25')

When label is only one, error quite different -

File "/usr/local/lib/python3.8/site-packages/prometheus_client/metrics.py", line 187, in remove

   del self._metrics[labelvalues]
   KeyError: ('Fail', )

Comma at the end of labelvalues confused me

从 prometheus_client/metrics.py 中第 187 行附近的 remove 实现开始，复现 issue 中的两个标签数量示例。检查现有的 metric 测试，确认其中涵盖了 child 删除和缺失标签元组的情况。当删除 child 时的预期行为已由测试覆盖，并反映在 issue 的结果中时，即可视为完成。