The first argument of most, if not all user defined function is a converter
object. This object gives access to methods to get information on the
conversion context and to methods useful for the conversion, both as an HTML
converter and as a generic Texinfo::Convert::Converter
(see (texi2any_internals)Texinfo::Convert::Converter Helper methods). The
converter can be used for error reporting by using
Texinfo::Convert::Converter methods. See Error Reporting in User Defined Functions on error reporting.
The converter can also be used for in-document strings translation.
See Translations in Output and Customization on translated strings in output.