docs: public static Builder newSchema(GraphQLSchema existingSchema) {
          return new Builder()
                  .query(existingSchema.getQueryType())
                  .mutation(existingSchema.getMutationType())
                  .subscription(existingSchema.getSubscriptionType())
                  .codeRegistry(existingSchema.getCodeRegistry())
                  .clearAdditionalTypes()
                  .clearDirectives()
                  .additionalDirectives(existingSchema.directives)
                  .additionalTypes(existingSchema.additionalTypes);
      }