Remove _clear() in DataClusters class

[stevenhua0320]

No description provided.

[sbillinge]

It should not be needed but make sure the behavior doesn't change when we do that

[Ainamacar]

This should be OK if incorporating its functionality into init, that is the only call to _clear().

I had originally made this a public member so classes in other modules that had a DataClusters member could use it when they cleared their members. However, in the existing implementation all instances of DataClusters are local variables that are created when needed and drop out of scope when not, so that functionality never came up.

[sbillinge]

Thanks @Ainamacar . We normally try and keep the the code simple so let's leave this as an open issue. It is not high priority. Just general code hygiene that we note down when we find it and clean up from time to time.