lib/zendesk_api/collection.rb
def <<(item)
      fetch

      if item.is_a?(Resource)
        if item.is_a?(@resource_class)
          @resources << item
        else
          raise "this collection is for #{@resource_class}"
        end
      else
        @resources << wrap_resource(item, true)
      end
    end
def <<(item)
      fetch

      if item.is_a?(Resource)
        if item.is_a?(@resource_class)
          @resources << item
        else
          raise "this collection is for #{@resource_class}"
        end
      else
        @resources << wrap_resource(item, true)
      end
    end
Adds an item to this collection
 @option item [ZendeskAPI::Data] the resource to add
 @raise [ArgumentError] if the resource doesn't belong in this collection