names = set()
for input in hou.pwd().inputs():
    geo = input.geometry()
    for attribs in geo.pointAttribs(), geo.vertexAttribs():
        names.update([a.name() for a in attribs if a.dataType() == hou.attribData.Float])
return [x for pair in [(n, n) for n in sorted(names)] for x in pair]

Codec AVOption apply_trc (color transfer characteristics to apply to EXR linear input) specified for input file #0 ([i]"path to framelist"[/i]) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some decoder which was not actually used for any stream.

GIF muxer supports only a single video GIF stream.
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:0 -- 
Conversion failed!

convert-to-GIF(){
    for ARG in $@; do
        file=$ARG
        file_name=${file%.*}
        palette="/tmp/palette.png"
        ffmpeg -y -i $file -vf fps=10,scale=500:-1:flags=lanczos,palettegen $palette
        ffmpeg    -i $file -i $palette -filter_complex "fps=10,scale=500:-1:flags=lanczos[x];[x][1:v]paletteuse" $file_name.gif
    done
    }

vector v0 = normalize(set(-1,0,-1));
vector vref = set(0,0,-1);

vector4 orient = dihedral(v0, vref);
vector angle = qconvert(orient);

angle = degrees(angle)*-1;
v@angle = angle;