Return tool in the shape of the converter format names.
format is one of TOOL_FORMATS; these ids name converters and are
separate from the listing styles. Throws OCToolError for an
unknown id rather than falling back, since the output would be for the
wrong target.
Return
toolin the shape of the converterformatnames.formatis one of TOOL_FORMATS; these ids name converters and are separate from the listing styles. Throws OCToolError for an unknown id rather than falling back, since the output would be for the wrong target.