code: def get_attachment(opts)
        opts = opts.clone
        [:attachment_ids].each do |k|
          validate_param(opts, k, true)
        end
        req = build_soap! do |type, builder|
          if(type == :header)
          else
            builder.nbuild.GetAttachment {|x|
              builder.nbuild.parent.default_namespace = @default_ns
              builder.attachment_ids!(opts[:attachment_ids])
            }
          end
        end
        do_soap_request(req)
      end
docs: ----------- Attachment Operations ----------
   Used to retrieve existing attachments on items in the Exchange store
   @see http://msdn.microsoft.com/en-us/library/aa494316.aspx
   @param [Hash] opts
   @option opts [Array] :attachment_ids Attachment Ids to fetch
   @option opts [Hash] :attachment_shape Attachment shape
     include_mime_content: true or false (optional)
     body_type: "Best" | "HTML" | "Text" (optional)
     filter_html_content: true or false  (optional)
     additional_properties:  @todo finish implementation