Get reusable workflows in sharepoint library using powershell

I have powershell that traverses each library in entire site collection to find document count in libraries with some other additional useful information.

One of the information fetched is workflow count and names of workflows in library.

Below script gives me list of custom workflow added in library as well as OOTB workflows

                                            foreach ($wf in $Library.WorkFlowAssociations)
                                            {
                                                   if($wf.Name -notlike "*Previous Version*")
                                                   {     
                                                         write-host "Workflow -->" $wf.Name
                                                   }
                                            }

Script fails to list down any reusable workflow added in library.

Is there any other method which will list all workflows along with reusable ones.

Ratnadeep Raul