code: public B camundaInSourceExpressionTarget(String sourceExpression, String target) {
      CamundaIn param = modelInstance.newInstance(CamundaIn.class);
  
      param.setCamundaSourceExpression(sourceExpression);
      param.setCamundaTarget(target);
  
      addExtensionElement(param);
  
      return myself;
    }
docs: Sets a "camunda:in" parameter to pass an expression from the signal-throwing
  process instance to a variable in the signal-catching process instance
  
  @param sourceExpression the expression in the signal-throwing process instance
  @param target the name of the variable in the signal-catching process instance
  @return the builder object