When I invoke `dot -T?`, the `pdf` format is only listed in Debian
trixie (stable) and sid (unstable) but not in forky (testing):

    $ docker run --rm -it debian:stable
    root@8b1f397565dc:/# dot -V
    dot - graphviz version 2.42.4 (0)
    root@dcaafc51a6d7:/# dot -T?
    Format: "?" not recognized. Use one of: canon cmap cmapx cmapx_np dot dot_json eps fig gd gd2 gif gv imap imap_np ismap jpe jpeg jpg json json0 mp pdf pic plain plain-ext png pov ps ps2 svg svgz tk vdx vml vmlz vrml wbmp webp x11 xdot xdot1.2 xdot1.4 xdot_json xlib

    $ docker run --rm -it debian:testing
    root@8b1f397565dc:/# dot -V
    dot - graphviz version 14.0.5 (0)
    root@8b1f397565dc:/# dot -T?
    Format: "?" not recognized. Use one of: canon cmap cmapx cmapx_np dot dot_json eps fig gd gd2 gif gv imap imap_np ismap jpe jpeg jpg json json0 pic plain plain-ext png pov ps ps2 svg svg_inline svgz tk vrml wbmp xdot xdot1.2 xdot1.4 xdot_json

    $ docker run --rm -it debian:unstable
    root@8b1f397565dc:/# dot -V
    dot - graphviz version 14.1.1 (0)
    root@8b1f397565dc:/# dot -T?
    Format: "?" not recognized. Use one of: canon cmap cmapx cmapx_np dot dot_json eps fig gd gd2 gif gv imap imap_np ismap jpe jpeg jpg json json0 pdf pic plain plain-ext png pov ps ps2 svg svg_inline svgz tk vrml wbmp xdot xdot1.2 xdot1.4 xdot_json

For some GraphViz users, myself included, this is a breaking bug.
Switching to a different intermediate format for subsequent PDF
conversion is non-trivial and often changes the visual output.