Jenkins rollback with scripted pipeline

node {
   // Check the input build no exits or not 
    stage('Check the Valid Build Number') { // for display purposes
     
        def jenkins = Jenkins.getInstance()
        def jobName = "Demo"
        def job = jenkins.getItem(jobName)
        def BuildNo = "${BUILD_NUMBER}"
        println "Last successfull build: ${job.getLastSuccessfulBuild()}"
        def allbuild = "${job.getBuilds().collect{ it.getNumber()}}"
        if(allbuild.contains(BuildNo)){
            println "We found the build number entered by you in the build history: ${BuildNo}"
        } 
        else 
        {
            println "No build number was found "
            error("Build failed because of this and that..")

        }
        
        
    }

    stage('Rollback to Dev') {
         println "Rollback to Dev is completed"
    }
    
    
}