code: public SoySauceBuilder withPluginInstances(Map<String, Supplier<Object>> pluginInstances) {
      this.userPluginInstances = ImmutableMap.copyOf(pluginInstances);
      return this;
    }
docs: Sets the plugin instance factories, to be used when constructing the SoySauce.
  
  <p>These are used to supply the runtime instances needed by SoyJavaSourceFunction
  implementations which use the {@code callInstanceMethod} API.