class ActiveFedora::Base

def rels_ext

Failing that, creates a new RelsExtDatastream and adds it to the object
Failing that, attempts to load from Fedora and addst to in-memory datastreams
Tries to grab from in-memory datastreams first
Returns the RELS-EXT Datastream 
def rels_ext
  if !datastreams.has_key?("RELS-EXT") 
    add_datastream(ActiveFedora::RelsExtDatastream.new)
  end
  return datastreams["RELS-EXT"]
end