Calling an activity in an expression

The standard function callActivity( ) in the Pega-RULES Utilities library calls an activity, but returns only void, not a value result. You can execute an activity in an expression, but only for its side effects. Identify the primary page, the activity, and the parameter page. For example:

@Pega-RULES:Utilities.callActivity(pyWorkPage, MyActivity, tools.getParameterPage());