Fuzzy call graphs

f (maybe) calls g if g.name is in f.body

This gives false positives

python call_graph.py "${ABS_PATH_OF_MODULE}" > module_callgraph.gv \
  && dot -Tpdf module_callgraph.gv -o module_callgraph.pdf \
  && open module_callgraph.pdf

(Where dot is from https://www.graphviz.org/documentation/)