Computation_watcher.For_testingval log_model_action_monitor :
sexp_of_model:('model -> Core.Sexp.t) ->
?sexp_of_action:('action -> Core.Sexp.t) ->
?action:'action option ->
?info_string_prefix:string ->
model_before:'model ->
model_after:'model ->
config:Config.t ->
unit ->
string