code: def visualize(ctx, meta_model_file, model_file, ignore_case, output_format):
      
      debug = ctx.obj['debug']
      meta_model, model = check_model(meta_model_file,
                                      model_file, debug, ignore_case)
      if output_format == 'plantuml':
          pu_file = "{}.pu".format(meta_model_file)
          click.echo("Generating '{}' file for meta-model.".format(pu_file))
          click.echo("To convert to png run 'plantuml {}'".format(pu_file))
          click.echo("To convert to svg run 'plantuml -tsvg {}'".format(pu_file))
          metamodel_export(meta_model, pu_file, PlantUmlRenderer())
      else:
          dot_file = "{}.dot".format(meta_model_file)
          click.echo("Generating '{}' file for meta-model.".format(dot_file))
          click.echo("To convert to png run 'dot -Tpng -O {}'".format(dot_file))
          metamodel_export(meta_model, dot_file)
  
      if model_file:
          if output_format == 'plantuml':
              raise Exception("plantuml is not supported for model files, yet.")
          dot_file = "{}.dot".format(model_file)
          click.echo("Generating '{}' file for model.".format(model_file))
          click.echo(
              "To convert to png run 'dot -Tpng -O {}'".format(model_file))
          model_export(model, dot_file)
docs: Generate .dot file(s) from meta-model and optionally model.