java.lang.InstantiationException error when executing class in Groovy Soap UI 5.4.0

trying to execute a Groovy script in SOAPUI 5.4.0

class MyClass {
// The three following fields are MANDATORY
def log 
def context
def testRunner

public  MyClass(log,context,testRunner){
    this.log = log 
    this.context = context
    this.testRunner = testRunner
    }
    def MyMethod(){log.info "Reference Groovy function file" }
}

and receiving error i.e.

groovy.lang.GroovyRuntimeException: Failed to create Script instance for class: class MyClass. Reason: java.lang.InstantiationException: MyClass

same code was working in previous soap ui version , could you please help.