message: remove use in private api
diff: @@ -14,7 +14,7 @@ export class StylableContext {
  this.generator = new Generator({...config, resolver: this.resolver});
  }
  add(sheet: Stylesheet) {
  - (this.generator as any).config.resolver.zMap[sheet.namespace] = sheet;
  + this.resolver.add(sheet.namespace, sheet);
  this.sheets.push(sheet);
  }
  registerMixin(name: string, mixin: Function) {
  