anchor.diff:  
   == Plugin Tutorial
   
  -We provide a _sample_ https://github.com/killbill/killbill-custom-invoice-formatter-example[custom invoice formatter] plugin. Let us now take a closer look at how you can create a similar custom plugin.
  +We provide a _sample_ https://github.com/killbill/killbill-custom-invoice-formatter-example[custom invoice formatter] plugin. You can use this as a starting point for developing your plugin. Let us now take a closer look at how you can create a similar custom plugin.
   
   === Initial Setup
   
  
positive.code: ```
  
  * The `CustomInvoiceFormatterFactory` implements the `org.killbill.billing.plugin.notification.api.InvoiceFormatterFactory` interface. 
  
  * It has a default constructor as shown above.
  
  * It has a `createInvoiceFormatter` formatter method that creates and returns a `CustomInvoiceFormatter` object.
  
  
negative.code: ```
  * The `CustomInvoiceFormatter` class extends `org.killbill.billing.plugin.notification.generator.formatters.DefaultInvoiceFormatter`.
  
  * A field called `newInvoiceMessage` is defined. This is a custom field. It has a corresponding `getNewInvoiceMessage` method.
  
  * You can add other custom fields as required. For each field, ensure that the field is initialized and that there is a `getter` method that returns the value of the field. 
  