Detaches current metric from the engine and no metric’s computation is done during the run.
This method in conjunction with attach() can be useful if several
metrics need to be computed with different periods. For example, one metric is computed every training epoch
and another metric (e.g. more expensive one) is done every n-th training epoch.
engine: the engine from which the metric must be detached
usage: the usage of the metric. Valid string values should be