anchor.diff:  * reusable (optional): If set to `true`, then it is allowed to register a metric multiple times under the same name.
   Note that all such instances must set `reusable` to `true`.
   Default is `false`.
  -The implementation must throw an `IllegalArgumentException` in case an attempt is made to register a metric multiple times where not all instances
  -are marked as reusable.
  -See also <<reusing_of_metrics>>.
  +See <<reusing_of_metrics>> for more details.
   
   Metadata must not change over the lifetime of a process (i.e. it is not allowed
   to return the units as seconds in one retrieval and as hours in a subsequent one).
  
positive.code: 
  If this behaviour is required, then it is possible to mark all such instances as _reusable_ by passing
  the respective flag via Metadata or field in the Annotation. Gauges are not reusable.
  
  Only metrics of the same type can be reused under the same name.
  Trying to reuse a name for different types will result in an `IllegalArgumentException`.
  
negative.code: ** The implementation must throw an `IllegalArgumentException` when the metric is rejected.
  ** It is not allowed to reuse a metric (name) for metrics of different types.
  The implementation must throw an `IllegalArgumentException` if such a mismatch is detected.
  ** See <<reusing_of_metrics>> for more details.
  
  
  === Base Package
  