The built-in exporters (pdf, epub, html-single) all assume that the command being run recognizes the `-a` option flag as a document attribute assignment. While this is true for Asciidoctor-based converters, this may not be true for all converters. The name of the option flag should be configurable in the `build` section of the Assembler configuration file. The proposed key name is `attribute_option_flag`. For example: ``` build: command: my-asciidoc-converter attribute_option_flag: '--attribute' ``` The `<name>=<value>` will be added after the flag each time it is used.