Returns a structural DAG of the fitted model: nodes for the response,
each predictor, each parameter (mu, sigma, ...), and any random-effect
grouping variables; edges connecting predictors to the parameters they
enter, parameters to the response, and groups to their random-effect
contribution. The returned object is an S3 list with nodes and
edges tibbles plus a generated DOT-language string.
Rendering live needs a downstream tool that consumes DOT - the
DiagrammeR package (which symbolizer does NOT require) is one
option; pasting as_dag(sym)$dot into https://dreampuf.github.io/GraphvizOnline/
is another. The S3 print method shows the DOT string and a brief
summary; as_dag(sym)$nodes and $edges are the raw tables.
This is a structural surface - it visualises how the symbolic
object connects predictors, parameters, and the response. It does
not show coefficient values; for those see
parameter_interpretation().