MavenProjectBuilder injection in a Mojo

[Sebastien Brunot]

Hi all,
 
what is the expression to use for injection of an
org.apache.maven.project.DefaultMavenProjectBuilder instance as the
value of a pojo parameter:
 
/**

* A MavenProjectBuilder instance

* 

* @parameter expression="????"

* @readonly

* @required

*/

private MavenProjectBuilder projectBuilder;

what should i set as expression ?
 
Thanks for your help,
 
Sebastien