Volumes that are provisioned with `VolumeMode: Block` often have a
MetrucsProvider interface declared in their type. However, the
MetricsProvider should implement a GetMetrics() function. In the cases
where the storage drivers do not implement GetMetrics(), a panic can
occur.
Usual type-assertions are not sufficient in this case. All assertions
assume the interface is present. There is no straight forward way to
verify that a valid GetMetrics() function is provided.
By adding SupportsMetrics(), storage driver implementations require
careful reviewing for metrics support.
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