    # File lib/fog/ecloud/collection.rb, line 10
          def check_href!(opts = {})
            unless href
              opts = { :parent => opts } if opts.is_a?(String)
              msg = ":href missing, call with a :href pointing to #{if opts[:message]
                      opts[:message]
                    elsif opts[:parent]
                      "the #{opts[:parent]} whos #{self.class.to_s.split('::').last.downcase} you want to enumerate"
                    else
                      "the resource"
                    end}"
              raise Fog::Errors::Error.new(msg)
            end
          end