def find_providers_for(attributes)
      plugins = []
      attributes.each do |attribute|
        attrs = select_subtree(@map, attribute)
        raise Ohai::Exceptions::AttributeNotFound, "No such attribute: \'#{attribute}\'" unless attrs
        raise Ohai::Exceptions::ProviderNotFound, "Cannot find plugin providing attribute: \'#{attribute}\'" unless attrs[:_plugins]
        plugins += attrs[:_plugins]
      end
      plugins.uniq
    end
def find_providers_for(attributes)
      plugins = []
      attributes.each do |attribute|
        attrs = select_subtree(@map, attribute)
        raise Ohai::Exceptions::AttributeNotFound, "No such attribute: \'#{attribute}\'" unless attrs
        raise Ohai::Exceptions::ProviderNotFound, "Cannot find plugin providing attribute: \'#{attribute}\'" unless attrs[:_plugins]
        plugins += attrs[:_plugins]
      end
      plugins.uniq
    end
gather plugins providing exactly the attributes listed