Comment 1 for bug 745669

From graphviz-2.26.3 Changelog:
December 10, 2009
        - Release 2.26.0
        - Core features:
                - added: "smyrna" - a new opengl-based viewer for large graphs
                - added: rudimentary "gml2gv", "gv2gml" converters
                - extended support for various image formats in node images
                - removed vestiges of codegens, now all putput formats supported
                  through plugins. Dropped some output formats for which
                  plugins have not been developed: -Tdia, -Tmif

It was removed upstream, but out of date documentation lingers - even on graphviz.org