Converting dates in drools workbench decision rule template

Question

Hi I have been trying with drools decision rule templates. I have tried converting between dates in drools decision template. The template is shown below.

The generated rule is shown below.

package com.myspace.sample;
import java.time.format.DateTimeFormatter;

rule "DataUnification_0"
    dialect "mvel"
    when
        cus : Customer( )
        data : Data( dateOfBirth != null )
        DateTimeFormatter( )
    then
        modify( cus ) {
                setDateOfBirth( data.dateOfBirth.format(DateTimeFormatter.ofPattern("dd-MMM-yy")) )
        }
end

But when trying to validate error is thrown as below.

[KBase: defaultKieBase]: Unable to Analyse Expression @Modify with( cus ) { setDateOfBirth( data.dateOfBirth.format(DateTimeFormatter.ofPattern("dd-MMM-yy")) ) };: [Error: unable to resolve method using strict-mode: com.myspace.sample.Customer.setDateOfBirth(java.lang.String)] [Near : {... fy with( cus ) { setDateOfBirth( data.dateOfBir ....}] ^ [Line: 5, Column: 0]

The date formatter wasn't available in the initial list of objects. I added it to external objects in the projects. Is there anyway to solve this problem?