Use get() instead of the deprecated getInstance() to access to the jenkins singleton.

Jenkinsfile

@@ -21,7 +21,7 @@ pipeline {
         stage('walking projects') {
             steps {
                script {
-                    Jenkins.getInstance().getAllItems(TopLevelItem.class).each { p ->
+                    Jenkins.get().getAllItems(TopLevelItem.class).each { p ->
                             projects2artifacts[p.name] = []
                             p.getAllJobs().each { j -> projects2artifacts[p.name] << j.name; artifacts2projects[j.name] = p.name }
                     }
@@ -35,7 +35,7 @@ pipeline {
             steps {
                 script {
                     // get all the maven modules and their dependencies
-                    Jenkins.getInstance().getAllItems(hudson.maven.MavenModule.class).each { m ->
+                    Jenkins.get().getAllItems(hudson.maven.MavenModule.class).each { m ->
                             modules2deps[m.name] = []
                             m.getDependencies().each { d -> modules2deps[m.name] << "${d.groupId}:${d.artifactId}" }
                     }

README.md

@@ -11,4 +11,7 @@ Given a Jenkins project P:
 * [Pipeline: Maven](https://plugins.jenkins.io/pipeline-maven)
 * [Pipeline: Basic Steps](https://plugins.jenkins.io/workflow-basic-steps) 
 * [Pipeline: Dependency Walker](https://plugins.jenkins.io/pipeline-dependency-walker/) 
-* [NodeLabelParameter](https://plugins.jenkins.io/nodelabelparameter) (to allow to dynamically select the node on which a job should be executed)
+
+## Documentation
+* [jenkins.model.Jenkins](https://javadoc.jenkins-ci.org/jenkins/model/Jenkins.html)
+* [jenkins.model.ItemGroup](https://javadoc.jenkins-ci.org/hudson/model/ItemGroup.html)