ember view select unique values

In ember 1.10 I have a dropdown- select and options of a list of clients. These clients are parents of environments. Selecting a client will populate another dropdown with the its children environments. How do I restrict the clients select to only unique values?

Here's my dropdown:

{{view "select" content=model 
  optionValuePath="content.clientId" 
  optionLabelPath="content.clientName"}}

Thanks for your help!