Chef and ruby: how to convert a array into a set -

I have an array that looks like this:

  nodes = ['server 1 '' server1 ',' server2 ']   
 In a chef recipe, I have to convert the set before going to a template ARB. How do i do this   
 
 
 This works with pattern set, matrix, JSON etc; This is the first try.  
  'Set' nodes are required [['server1', 'server1', 'server2'] p nodes.to_set # # & lt; Set: {"server1", "server2"} & gt;