We understand GML as described in the gephi documentation. gephi 
There is talk of a specification but these are dead links.
Convert a .graph.json or .schema.json file to a gml file with a single command line with five parts.
- the deno command to run a program - the permissions granted to deno for this program - the internet address of the program - the path to the file to be converted - the redirection of output to a file in GML format
Here we show an example with each of these parts on a separate line. We proceed each newline with a backslash to indicate they should be ignored.
deno run \ --allow-read \ http://hsc.fed.wiki/assets/gml.js \ sample.graph.json \ > sample.gml