def param_or_field(key)

      key = key.to_s

      (h.fields['params'] || {})[key] || h.fields[key]
    end
def param_or_field(key)

      key = key.to_s

      (h.fields['params'] || {})[key] || h.fields[key]
    end
Sometimes a value is passed as a[n expression] parameter or as a
 workitem field, with priority to the parameter.

   sequence do
     set 'f:country' => 'uruguay'
     participant 'toto'
       # in toto, workitem.param_or_field(:country) will yield 'uruguay'
     participant 'toto', :country => 'argentina'
       # workitem.param_or_field(:country) will yield 'argentina'
   end