(bug): TypeError: Viz is not a function

[vogloblinsky]

Calling ngd-transformer directly for a simple module of an angular application breaks with :
Viz is not a function at DotEngine.generateSVG (/home/vogloblinsky/Documents/www/TMP/compodoc/compodoc/node_modules/@compodoc/ngd-transformer/dist/engines/dot/dot.js:179:22)

Reproduced with a simple Node.js script, using twice new ngdT.DotEngine().

Moving viz.js require from this line https://github.com/compodoc/ngd/blob/master/src/modules/transformer/src/engines/dot/dot.ts#L227 to the top https://github.com/compodoc/ngd/blob/master/src/modules/transformer/src/engines/dot/dot.ts#L4 solve the issue.